Solar Orbiter - IRIS - ADITYA - Joint Workshop

15 Mar 2026, 18:00 → 20 Mar 2026, 16:00 Europe/Berlin

Harnack Haus (Berlin)

Solar science is going through an exciting period with new space missions complementing each other and extending the capabilities of proven ones. This leads us to the discovery of new solar phenomena and a better understanding of important physical processes. We invite the community to present and discuss the big advances in scientific understanding and the many discoveries coming out of three such missions,  the Solar Orbiter of ESA and NASA, IRIS of NASA, and Aditya of ISRO at the 10^th Solar Orbiter, 18^th IRIS, and 1^st Aditya workshop. It shall take place from 16^th to 19^th March, 2026, at the Harnack House of the Max Planck Society in the vibrant city of Berlin. You are invited to join, share your results, learn what colleagues have found, and get to know the new research possibilities opened up by combining the capabilities of these exciting missions. The workshop will cover topics ranging from the interior of the Sun to the heliosphere and will highlight the role of the magnetic field in shaping solar activity.

SOW2026_poster.pdf

Sunday 15 March

Registration

Monday 16 March

Registration

Opening Remarks and Welcome

Dynamos, production and the evolution of the magnetic field

1 The small-scale solar dynamo

First Name: Matthias
Last Name: Rempel
Email Address: rempel@ucar.edu
Affiliation: High Altitude Observatory, NSF National Center for Atmospheric Research

All Authors: Matthias Rempel

Abstract: The Sun is a unique star in the sense that we can observe it at high resolution and study phenomena at a detail that is hidden in stellar observations. This applies specifically to small-scale magnetic fields that are organized on the stellar surface on scale of granulation and smaller. Observations have shown that these small-scale magnetic fields are ubiquitous in the solar atmosphere and appear to be mostly independent of the solar sunspot cycle, which provides strong support for a small-scale magnetic dynamo. In this talk I will provide an overview of developments over the past 10-20 years. Recent research has clarified the role of the magnetic Prandtl number for small-scale dynamo action during both kinematic and saturated phase of dynamo operation and demonstrated that the low Pm found in stellar convection zones does not prevent small-scale dynamo operation as thought earlier. Simulations of strongly stratified convection point to a small-scale dynamo that operates over a wide range of scales in the solar convection zone and produces a magnetic field of a large enough strength to have a dynamical impact on convection. I discuss implications for the convection zone as well as heating of the solar atmosphere.

Speaker: Matthias Rempel (High Altitude Observatory, NSF National Center for Atmospheric Research)

2 Nearly continuous monitoring of active region nesting with Solar Orbiter: Towards long-term forecasting of solar activity

First Name: Adam
Last Name: Finley
Email Address: adam.finley.astro@gmail.com
Affiliation: ESA/ESTEC

All Authors: Adam J. Finley

Abstract: The repeated emergence of active regions in close proximity to one another creates long-lived sources of solar activity called active nests. These nests are thought to form due to non-axisymmetries in the generation and storage of the Sun's dynamo magnetic field which preferences flux emergence at certain Carrington longitudes. Nesting is also observed on other Sun-like stars, suggesting that this is a fundamental process related to the global dynamo. Our ability to study the evolution of solar active nests is limited by our view from Earth. With Solar Orbiter monitoring the Sun's far-side for several months each year, multi-viewpoint observations (akin to the STEREO-AB era) now provide a pathway to study the formation and evolution of active nests. An active nest in 2022 was shown to be a prolific flare factory, producing 50-70% of all solar flares over the entire solar surface for five months (in the nearly continuous monitoring window). The repeated emergence of active regions formed more complex regions (Hale classifications) with a higher occurrence rate of solar flares. Similarly, in 2024, the collision of two active nests built complexity and triggered a dramatic intensification of their flaring activity. Active region nesting also structures the solar corona which could be leveraged for long-term planning of solar wind connection science. In future, short to medium-term space weather forecasting will benefit from the improved identification and monitoring of active nests.

Speaker: Adam Finley (ESA/ESTEC)

Session1_Finley.pdf

3 Studying Solar Hemispheric Magnetic Flux variations using Synoptic Maps and SO/PHI Far-Side Observations

First Name: Hanna
Last Name: Strecker
Email Address: streckerh@iaa.es
Affiliation: Instituto de Astrofísica de Andalucía (IAA-CSIC) and Spanish Space Solar Physics Consortium, Granada, Spain

All Authors: David Orozco Suárez; Instituto de Astrofísica de Andalucía (IAA-CSIC) and Spanish Space Solar Physics Consortium, Granada, Spain; Gherardo Valori; MPS Göttingen, Germany; Artem Ulyanov; MPS, Göttingen, Germany; Sami Solanki, MPS, Göttingen, Germany; Johann Hirzberger; MPS, Göttingen, Germany; Julian Blanco Rodríguez; Universitat de València and Spanish Space Solar Physics Consortium, Valencia, Spain; Daniele Calchetti; MPS, Göttingen, Germany; Sami Solanki, MPS, Göttingen, Germany; Jose Carlos del Toro Iniesta, Instituto de Astrofísica de Andalucía (IAA-CSIC) and Spanish Space Solar Physics Consortium, Granada, Spain; And the SO/PHI team

Abstract: The magnetic flux distribution on the solar surface is typically reconstructed from Earth-based observations over one Carrington rotation, yet synoptic maps cannot directly capture the magnetic field on the far side of the Sun. In this study, we combine magnetic flux distributions from Earth-based observatories with far-side measurements from SO/PHI to evaluate how well the synoptic reconstruction represents the true flux on the hidden hemisphere. The Solar Orbiter mission, currently in operations for over five years during which it has passed five superior conjunctions provides repeated and unique far-side coverage during the rising phase of the solar cycle. We identify active regions observed by SO/PHI on the far side, determine their magnetic flux and field strength, and compare these values with the flux in synoptic maps for the corresponding Carrington rotations. This approach allows us to measure systematic under- or over-estimation of far-side magnetic features and to assess the role of persistent active longitudes. Our results quantify the far-side flux not captured in synoptic maps and underline the importance of Solar Orbiter’s viewpoint for improving global magnetic field models.

Speaker: Hanna Strecker (Instituto de Astrofísica de Andalucía (IAA-CSIC))

4 online – The Key Role of the Sun’s Polar and Surface Fields in the Global Dynamo

First Name: Jie
Last Name: Jiang
Email Address: jiejiang@buaa.edu.cn
Affiliation: Beihang University, China

All Authors: Jie Jiang

Abstract: Over 40 years of detailed solar magnetic field observations have shown that the original Babcock–Leighton (BL) dynamo scenario proposed in the 1960s could capture the essential physics of the global solar dynamo. That is the surface magnetic field, including the polar field, plays a central role in driving the solar cycle. In the past decade, major progress has been made in understanding the evolution of the solar surface magnetic field and incorporating this knowledge into dynamo modeling. The cycle dependence and stochastic properties of sunspot emergence, including their latitudes and tilt angles, have emerged as key sources of nonlinear and stochastic modulation of the solar cycle. When the observed surface magnetic field evolution is used to constrain the outer boundary condition of BL dynamo models, the resulting behavior differs fundamentally from the long-held flux transport dynamo framework developed in 1990s. Rather than relying on an equatorward meridional flow in the tachocline, the equatorward migration of the toroidal field arises naturally from the time- and latitude-dependent regeneration of toroidal flux, driven by latitudinal differential rotation together with the evolving surface field. Within this framework, the polar field strength becomes the primary regulator of the cycle period. In addition, the Lorentz force associated with the cyclic magnetic field produced by the dynamo naturally reproduces both the poleward and equatorward branches of the observed torsional oscillations.

Speaker: Jie Jiang (Beihang University, China)

Session1_Jiang.pdf

Coffee and Poster A

Magnetic field & impact on irradiance, atmosphere, etc.

5 Magnetic fields and modelling of irradiance variations

First Name: Theodosios
Last Name: Chatzistergos
Email Address: chatzistergos@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research, Göttingen, Germany

All Authors: Theodosios Chatzistergos

Abstract: Because direct measurements of solar irradiance exist only from the late 1970s onward, models are required to reconstruct earlier irradiance variations. On timescales from a day and longer, irradiance variations arise due to the evolution of the solar surface magnetic field, manifesting as dark sunspots and bright faculae and network. Accurate irradiance modelling therefore depends on reliable information about the distribution, and temporal evolution of surface magnetic features. Full-disc magnetograms from instruments such as KPVT, SoHO/MDI, and SDO/HMI provide direct measurements of the surface magnetic field since the 1970s, which is roughly the same period that direct measurements of irradiance exist. Ca II K archives can be used to produce unsigned magnetograms back to 1892, while reconstructions over earlier periods infer the solar magnetic field from sunspot or cosmogenic isotope data. Each of these datasets requires its own set of modelling assumptions, and different models handle these assumptions in different ways, leading to substantial discrepancies in their inferred secular trends. In this talk, I will provide an overview of the main approaches used to model solar irradiance and highlight recent advances.

Speaker: Theodosios Chatzistergos (Max Planck Institute for Solar System Research)

6 Stereoscopic disambiguation of solar vector magnetic fields using observations from SO/PHI and SDO/HMI

First Name: Xiang
Last Name: Li
Email Address: lixiang@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research

All Authors: Xiang Li, Gherardo Valori, Daniele Calchetti, Sami K. Solanki, Johann Hirzberger, Jonas Sinjan

Abstract: The solar vector magnetic field is inferred from spectropolarimetric observations of the polarization in magnetically sensitive spectral lines. However, the transverse component of the magnetic field has an 180° ambiguity in its orientation. Traditional single-view methods for resolving the ambiguity require assumptions on the properties of the photospheric magnetic field. Solar Orbiter (SO), and its onboard magnetograph (the Polarimetric and Helioseismic Imager, PHI), make it possible for the first time to avoid such assumptions, and to remove the ambiguity purely using observations from two vantage points. The Stereoscopic Disambiguation Method (SDM), which was developed based on this idea, has been successfully tested on simulated data and first science data from the High Resolution Telescope (SO/PHI-HRT) acquired in spring 2022. In this work, we applied the SDM to a number of SO/PHI-HRT datasets and corresponding datasets from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The SDM successfully disambiguates vector magnetograms in strong field areas, and for a large range of separation angles between the viewpoints. Quantitative diagnostic metrics were studied to evaluate the reliability of the SDM in localized areas. Furthermore, we compared the disambiguation results obtained by the SDM and the single-view disambiguation method.

Speaker: Xiang Li (Max Planck Institute for Solar System Research)

Session2_XiangLi.pdf

7 Influence of magnetic-field distribution on the spatio-temporal properties of EUV brightenings in the solar atmosphere

First Name: Nancy
Last Name: Narang
Email Address: nancy.narang@oma.be
Affiliation: Royal Observatory of Belgium

All Authors: Nancy Narang, Cis Verbeeck, David Berghmans, Marilena Mierla, Susanna Parenti, Pradeep Chitta, Daniele Calchetti, Frederic Auchere

Abstract: The extreme-ultraviolet (EUV) brightenings identified by Solar Orbiter, commonly known as “campfires”, are one of the fine-scale transient brightenings detected in the solar corona. Using closest-perihelion observations of Extreme-Ultraviolet Imager (EUI) onboard Solar Orbiter, recently we have reported the presence of smallest and shortest-lived EUV brightenings in the quiet-sun to date. We will present the spatio-temporal distribution of EUV brightenings over different magnetic environments of the solar atmosphere. By using various sets of quiet-sun and coronal-hole observations from HRIEUV/EUI we will present a comparative analysis of morphological and photometrical properties of EUV brightenings. We will discuss the interlinks of EUV brightenings to the photospheric dynamics and magnetic field distribution using HRT/PHI observations. Further their potential coupling through the solar atmosphere will be addressed using SPICE and IRIS observations.

Speaker: Nancy Narang (Royal Observatory of Belgium)

12:20 Lunch

Magnetic field & impact on irradiance, atmosphere, etc.

8 Impact of small-scale magnetic fields on the solar atmosphere

First Name: Milan
Last Name: Gosic
Email Address: mgosic.solar@gmail.com
Affiliation: LMSAL/SETI

All Authors: Milan Gosic

Abstract: The quiet regions of the solar surface are densely populated with small and weak magnetic flux patches. These patches contain an amount of magnetic flux comparable to what is found in active regions during the peak of the solar cycle. This suggests that these small-scale magnetic fields are essential components of solar magnetism and may play a critical role in the transport of mass and energy through the solar atmosphere. The magnetic flux of the quiet Sun (QS) is divided between network and internetwork features. Internetwork fields are found within the interiors of supergranular cells, while network fields outline the boundaries of these supergranules. Together, they create a dynamic environment where magnetic fields frequently emerge, move, and interact with one another. The spatiotemporal evolution of the QS magnetic fields is coupled to convective motions, leading to various processes that may contribute to chromospheric heating. These processes include, among others, the formation of vortices, the emergence and reconnection of magnetic field lines, and the generation of magnetohydrodynamic waves. In this talk, I will review our current results and understanding of QS magnetic activity and how it impacts the energetics and dynamics of the quiet solar atmosphere.

Speaker: Milan Gosic (LMSAL/SETI)

9 Probing the impact of viewing direction on the magnetic field evolution of an active region with SO/PHI and SDO/HMI

First Name: Jonas
Last Name: Sinjan
Affiliation: Max Planck Institute for Solar System Research

All Authors: Jonas Sinjan, Johann Hirzberger, Daniele Calchetti, Gherardo Valori, Xiaohong Li, Sami K. Solanki and the PHI team

Abstract: Active regions are the source region for the most energetic phenomena on the Sun. Maps of active regions’ photospheric magnetic fields, and derived quantities such as magnetic free energy and current density are often used as the primary inputs in flare forecasting models. One limitation of these magnetic field maps, and hence the derived quantities, is that they have always originated from observatories with the same singular view point: that from Earth. It is well known that the inference of the photospheric magnetic fields suffers off disc centre (heliocentric angles > 45-60 degrees), thus further restricting the time of reliable data for building forecasting models. With the Solar Orbiter mission, and the PHI instrument on board, during favourable orbital configurations, we can augment existing Earth-based observations and provide a longer coverage of reliable observations of an active region. Concurrently we can use these periods to investigate the true systematics of near limb observations now that a different vantage point is available. From 12 - 17th October 2023 Solar Orbiter observed an active region (NOAA 13465), initially separated from Earth by an angle of 80 degrees decreasing to 54 degrees. NOAA 13465 was just visible inside the East limb as seen by Earth at the start of the campaign. In this work we compare high resolution SO/PHI observations with the SHARP (Space Weather HMI Active Region Patches) maps from SDO/HMI. These observations provide a broad range of different viewing angles (μ=cos(θ)) between SO/PHI and SDO/HMI where one instrument can probe the impact of the viewing direction on the magnetic field inference.

Speaker: Jonas Sinjan (Max Planck Institute for Solar System Research)

Session1_Sinjan.pptx (owncloud.gwdg.de download link)

Chromosphere and transition region

10 Numerical modeling of the chromosphere and comparison with observations

First Name: Damien
Last Name: Przybylski
Email Address: przybylski@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research

All Authors: D. Przybylski

Abstract: The solar chromosphere presents a formidable modelling challenge. The coupling of the turbulent convection zone to the underlying magnetic field leads to it's highly dynamic nature, displaying spicules, shocks, swirls and jets. The large-scale magnetic topology further impacts the observed chromosphere. Finally a non-local thermodynamic equilibrium (NLTE) treatment is required. Capturing this multi-scale, multi-physics regime has long exceeded computational capabilities. With increasing computational power, 3D models are now able to include approximations to NLTE physics and non-equilibrium ionization. At the same time, larger simulations including more realistic magnetic topologies can be performed. Finally, spectral lines can be synthesised with 3D radiative transfer allowing for more accurate comparison between simulation and observation. In this contribution, we review current chromospheric modelling, outlining the capabilities and limitations. Models are now able to match the average line widths and intensities, yet discrepencies remain. We propose that a spatially resolved multi-height approach is now required to understand these differences, including the local magnetic field strength and flux imbalance, chromospheric lines and optically thin coronal observables.

Speaker: Damien Przybylski (Max Planck Institute for Solar System Research)

session_3_przybylski.pdf

11 Mg II Single-Peak Emission and Chromospheric Magnetic Fields Using IRIS and DKIST

First Name: João M.
Last Name: da Silva Santos
Email Address: jdasilvasantos@nso.edu
Affiliation: National Solar Observatory (USA)

All Authors: Joshua Bentley, Serena Criscuoli, Tom Schad, Momchil Molnar, Alex Pietrow, Bart De Pontieu, Juan Martinez-Sykora

Abstract: Single-peak Mg II h&k profiles are commonly observed in solar plage regions, and they are known to indicate hot, dense chromospheres. However, the magnetic field topology of the atmosphere where these profiles form remains poorly constrained. We analyze coordinated IRIS and DKIST observations from a recent joint campaign, combining IRIS ultraviolet spectroscopy with DKIST/ViSP spectropolarimetry to obtain magnetic field diagnostics across multiple atmospheric layers. We examine the spatial relationship between locations showing single-peak Mg II profiles and the underlying chromospheric and photospheric magnetic field components. We discuss whether the results are consistent with heating due to field line braiding.

Speaker: João da Silva Santos (National Solar Observatory (USA))

12 A study of synthetic Mg II h&k lines from a set of MURaM-ChE simulations

First Name: Patrick
Last Name: Ondratschek
Affiliation: Max Planck Institute for Solar System Research

All Authors: P. Ondratschek, D. Przybylski, H.N. Smitha, R. Cameron, S. K. Solanki

Abstract: The Mg II h&k lines are well-suited to study the solar chromosphere. Forming under non-local thermodynamic equilibrium conditions, the line formation of these lines is complicated and not fully understood. Theoretical models of the solar chromosphere, in combination with radiative transfer computations, are a necessary step for interpreting high-resolution observations from the Interface Region Imaging Spectrograph (IRIS) mission. In this work, we study synthetic Mg II h&k line profiles that are synthesized from a series of simulations. The simulations aim to represent the solar chromosphere at regions of varying magnetic flux. The simulations are computed with the recently developed chromospheric extension of the MURaM code (MURaM-ChE). The set of simulations ranges from a very quiet part of the Sun to a strong plage region. We aim to compare spectral line properties such as peak separation, peak intensity, and peak asymmetry ratio between the different models and observations. In addition, we discuss the effect of 3D radiative transfer in the different models.

Speaker: Patrick Ondratschek (Max Planck Institute for Solar System Research)

Coffee and Poster A

Chromosphere and transition region

13 online – Small-Scale Magnetic Reconnection in the Solar LowAtmosphere: Ubiquity, Transition-Region Heating, and Spicule Generation

First Name: Jayant
Last Name: Joshi
Email Address: jayant.joshi@iiap.res.in
Affiliation: Indian Institute of Astrophysics, Bengaluru

All Authors: Jayant Joshi

Abstract: Recent high-resolution observations reveal that small-scale magnetic reconnection in the solar lower atmosphere, manifested as quiet-Sun Ellerman bombs (QSEBs), is far more ubiquitous than previously recognised, with an estimated ∼750,000 events present across the quiet Sun at any given time. Using Hβ and Hε observations from the Swedish 1-m Solar Telescope, we identify widespread QSEBs characterised by rapid temporal variability and flame-like morphologies. A subset of these events shows clear signatures of energy deposition reaching higher atmospheric layers. This is indicated by co-spatial and co-temporal ultraviolet brightenings in the Si IV lines observed with the Interface Region Imaging Spectrograph, demonstrating that QSEBs can drive localized heating in the transition region. In addition, several QSEBs are temporally and spatially associated with the formation of type II spicules, supporting a scenario in which magnetic reconnection in the lower atmosphere contributes to the generation of spicules. While these effects are not universal, the observations establish QSEBs as an important mechanism for small-scale energy release, heating, and mass transport in the quiet Sun, highlighting their role in coupling the photosphere, chromosphere, and transition region.

Speaker: Jayant Joshi (Indian Institute of Astrophysics, Bengaluru)

14 Spicules in MURaM: Statistics, Structure, and Driving

First Name: Sanghita
Last Name: Chandra
Email Address: chandra@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research

All Authors: Sanghita Chandra, Robert Cameron, Damien Przybylski, Sami K. Solanki

Abstract: It has been suggested that spicules play a role in coronal heating, with reports of an association with transition region (e.g. Si IV emission) and coronal emission, observable in EUV passbands with Solar Orbiter. Understanding spicules has been difficult using observations alone. Realistic 3D simulations now help overcome these limits. We present the first statistical analysis of synthetic spicules from MURaM-ChE simulations, which reproduce key features of chromospheric dynamics. The non-equilibrium hydrogen treatment enables examination of 3D spicule geometry. Using a new Hα proxy, we identify numerous off-limb spicules and their on-disk counterparts in an enhanced-network simulation. We statistically analyze 58 spicules (types I and II) and compare them with earlier studies using Ca II H and Hα observations. The synthetic spicules show morphological properties and lifetimes broadly consistent with observations. To probe the underlying structure, we examine selected spicules using the Hα-proxy opacity. One illustrative spicule, with an apparent 190 km/s velocity, shows a sheet-like morphology. We demonstrate that such extreme apparent speeds arise not from true mass motion but from a rippling plasma sheet seen along the line of sight. The sheet lies at a quasi-separatrix layer (QSL). Whether a spicule appears sheet- or tube-like depends strongly on the Doppler shift used for observation, and their on-disk counterparts often display structures distinct from the spicules themselves. We synthesize 174 ˚A emission to assess the spicules’ multi-thermal nature which enables comparison with Solar Orbiter /EUI.

Speaker: Sanghita Chandra (Max Planck Institute for Solar System Research)

Session3_Chandra.pptx

15 online – Generation of Data Products for the Solar Ultraviolet Imaging Telescope (SUIT)

First Name: Janmejoy
Last Name: Sarkar
Email Address: sarkarjj@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research and IUCAA

All Authors: Janmejoy Sarkar, VN Nived, Soumya Roy, Rahul Gopalakrishnan, Rushikesh Deogaonkar, Sreejith Padinhatteeri, Durgesh Tripathi, A.N. Ramaprakash, Achim Gandorfer, Sami Solanki.

Abstract: The Solar Ultraviolet Imaging Telescope (SUIT) on board Aditya-L1 makes full-disk observations of the Sun in eleven filters within the 200-400 nm wavelength band. The spacecraft maintains a halo orbit around the Sun-Earth L1 point, enabling SUIT to take continuous observations of the solar photosphere and chromosphere. The raw data downloaded from the spacecraft is processed to generate science-ready Level-1 data, which is currently available for public use. The initial level of processing involves dark and bias corrections, flat-fielding, and stray light correction. The level 1 processing also implements the coordinate system on the image data, which is necessary for easy co-registration of SUIT images with data from other observatories. The Level-1 data is further processed to generate Level-2 data products. This stage of processing primarily includes morphological corrections, such as spot and contamination removal, spiked pixel removal, and image deconvolution for sharpening of morphological features. Additionally, the Level-2 processing toolkit will be publicly available, enabling end-users to process SUIT data with specific modules as needed. This presentation will cover the image calibration and processing of SUIT data, with a focus on generating Level 2 data products. We will also present the achieved level of correction and a quantitative account of the residual errors in the SUIT data products.

Speaker: Janmejoy Sarkar (Max Planck Institute for Solar System Research and IUCAA)

16 Non-thermal broadening in active regions

First Name: Kyuhyoun
Last Name: Cho
Email Address: kcho@seti.org
Affiliation: LMSAL / SETI

All Authors: Bart De Pontieu, Paola Testa

Abstract: Nonthermal broadening in spectral lines formed in the solar transition region has been a subject of interest for several decades, as its underlying mechanisms remain unclear and it may provide key insights into the heating of the upper solar atmosphere. Previous studies have primarily focused on the relationship between broadening and magnetic field orientation, often reporting that regions where the magnetic field is perpendicular to the line of sight exhibit higher broadening. This suggests that transverse waves, such as Alfven waves, may play a role in the nonthermal broadening. However, in this study, we present an opposite finding: higher broadening is observed in regions where the magnetic field is aligned with the line of sight. By analyzing the Si IV 1403 Å line in three plage regions observed by the Interface Region Imaging Spectrograph, we derived nonthermal velocity maps. These were compared to magnetic field inclination maps calculated via nonlinear force-free field extrapolation, based on vector magnetic fields from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. Our results clearly demonstrate that higher broadening is preferentially associated with lower-inclination regions showing downflows, highlighting the magnetic field-aligned component of nonthermal broadening. We interpret this finding as the presence of velocity gradients within plasma flowing downward along the magnetic field in the transition region.

Speaker: Kyuhyoun Cho (LMSAL / SETI)

260316_IRIS_workshop.pdf

17 Accessing the fine temporal scale of EUV brightenings and their quasi-periodic pulsations: 1 second cadence observations by Solar Orbiter/EUI

First Name: Daye
Last Name: Lim
Email Address: daye.lim@oma.be
Affiliation: Royal Observatory of Belgium and KU Leuven

All Authors: Daye Lim, Tom Van Doorsselaere, Nancy Narang, Laura A. Hayes, Emil Kraaikamp, Aadish Joshi, Konstantina Loumou, Cis Verbeeck, David Berghmans, and Krzysztof Barczynski

Abstract: Small-scale extreme-ultraviolet (EUV) transient brightenings are observationally abundant and critically important to investigate. Determining whether they share the same physical mechanisms as larger-scale flares would have significant implications for the coronal heating problem. A recent study has revealed that quasi-periodic pulsations (QPPs), a common feature in both solar and stellar flares, may also be present in EUV brightenings in the quiet Sun (QS). We aim to characterise the properties of EUV brightenings and their associated QPPs in both QS and active regions (ARs) using unprecedented 1 s cadence observations from Solar Orbiter’s Extreme Ultraviolet Imager (EUI). We applied an automated detection algorithm to analyse statistical properties of EUV brightenings. QPPs were identified using complementary techniques optimised for both stationary and non-stationary signals, including a Fourier-based method, ensemble empirical mode decomposition, and wavelet analysis. Over 500 000 and 300 000 brightenings were detected in ARs and QS regions, respectively. Brightenings with lifetimes shorter than 3 s were detected, demonstrating the importance of high temporal resolution. The QPP occurrence rates were approximately 11% in AR brightenings and 9% in QS brightenings, with non-stationary QPPs being more common than stationary ones. QPP periods span from 5 to over 500 s and show similar distributions between AR and QS. Moderate linear correlations were found between QPP periods and the lifetime and spatial scale of the associated brightenings, while no significant correlation was found with peak brightness. We found a consistent power-law scaling, with a weak correlation and a large spread, between QPP period and lifetime in EUV brightenings, solar, and stellar flares. The results support the interpretation that EUV brightenings may represent a small-scale manifestation of the same physical mechanisms driving larger solar and stellar flares. Furthermore, the similarity in the statistical properties of EUV brightenings and their associated QPPs between AR and QS regions suggests that the underlying generation mechanisms may not strongly depend on the large scale magnetic environment.

Speaker: Daye Lim (Royal Observatory of Belgium and KU Leuven)

Session3_Lim.pdf

18 Probing Transition Region–Solar Wind Connectivity with SPICE and SWA/HIS Instruments

First Name: Tania
Last Name: Varesano
Email Address: tania.varesano@colorado.edu
Affiliation: SWRI / CU Boulder

All Authors: Tania Varesano, Don Hassler, Yeimy Rivera, Joe Plowman

Abstract: The SPICE (Spectral Imaging of the Coronal Environment) and HIS (Heavy Ion Sensor) instruments on Solar Orbiter were designed to enable us to trace the source regions of elemental enrichment at the Sun into the heliosphere and examine the processes governing composition signatures in different solar wind regimes. We utilize EUV (Extreme Ultra-Violet) spectroscopic observations from SPICE aboard Solar Orbiter, analyzing emission lines from ions formed over a wide temperature range—from the upper chromosphere to the low corona. To extend our analysis beyond the solar atmosphere, we incorporate in-situ measurements from HIS, linking solar surface composition to solar wind outflows. Our investigation includes the evolution of relative elemental abundances in solar active regions (ARs) in the context of the first ionization potential (FIP) effect. Our objective is to characterize how abundance variations develop across solar structures and different atmospheric layers, and to understand their evolution when expanding out into the heliosphere. Preliminary results provide new insights into the coupling between magnetic structure, elemental fractionation, and solar wind composition—shedding light on how the FIP effect evolves and manifests in both the solar atmosphere and heliosphere.

Speaker: Tania Varesano (SWRI / CU Boulder)

Session3_TaniaVARESANO.pdf

Poster A

All these posters will be up on throughout both Monday and Tuesday, during both coffee breaks and the dedicated evening poster sessions.

Reception

Tuesday 17 March

Polar Science

19 The Sun’s Polar Magnetic Fields: Current Knowledge, Open Questions, and the Promise of SO/PHI

First Name: Gordon
Last Name: Petrie
Email Address: gpetrie@nso.edu
Affiliation: National Solar Observatory

All Authors: Gordon Petrie

Abstract: The Sun’s polar magnetic field is routinely measured from (near) Earth through full-disk synoptic programs and, less frequently, with high-resolution telescopes. These observations face inherent challenges: the large viewing angle toward the poles degrades effective spatial resolution, lowers signal-to-noise ratios, and places most of the nearly radial magnetic field into the transverse component, for which Zeeman sensitivity is substantially reduced. Although large telescopes can partially mitigate these limitations—albeit over small fields of view and with seeing challenges—the most direct solution is to observe from higher heliographic latitudes and closer proximity to the Sun. I will summarize polar field measurements from the SOLIS/VSM, Hinode/SOT/SP, and DKIST/ViSP spectropolarimeters, highlighting their respective strengths and limitations. I will also discuss the unique vantage and expected scientific return of SO/PHI, which is poised to transform our understanding of the polar magnetic field. As the first Solar Orbiter polar results become available, I will outline the mission’s contributions and the opportunities they present for advancing polar magnetism research.

Speaker: Gordon Petrie (National Solar Observatory)

20 Dynamic processes of the polar cap build-up

First Name: Kinga
Last Name: Albert
Email Address: albert@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research

All Authors: Kinga Albert, Johann Hirzberger, Gherardo Valori, Daniele Calchetti, L. P. Chitta, L. R. Bellot Rubio, J. Blanco Rodríguez, D. Orozco Suárez, S.k. Solanki and the PHI team

Abstract: In March 2025, we gained a new and exciting viewing angle of the Sun’s polar regions as Solar Orbiter left the ecliptic plane. Currently, it can observe the poles at up to 17◦ solar latitude compared to the maximum 7◦ view-angle from Earth. In this configuration, on March 21 and 22, we observed the South pole with the Polarimetric and Helioseismic Imager (SO/PHI), acquiring high cadence data for more than 14.5 hours. The campaign was supported by observations from the Extreme-Ultraviolet Imager (EUI) and the Spectral Imaging of the Coronal Environment (SPICE) instruments. Polar magnetic fields are crucial in refining our understanding of many solar processes and their relation with the heliosphere. With this unprecedented data set, we have a unique opportunity to study the small-scale dynamics that gradually contribute to the long-term build-up of the polar magnetic cap. We analyse data from the High Resolution Telescope of SO/PHI, identifying large magnetic concentrations associated with the developing polarity at the south pole. Using co-observations from the High-Resolution Imager of EUI, we apply a segmentation approach to identify the photospheric regions to which these concentrations are magnetically connected. With this information, we investigate the temporal evolution of the photospheric magnetic field: we track the changes of the concentrations that build up the polarity of the cap and their interactions with the surrounding fields, uncovering processes of flux emergence and cancellation driven by dynamics in the upper atmosphere.

Speaker: Kinga Albert (Max Planck Institute for Solar System Research)

Session4_Albert.pdf

21 The first out-of-ecliptic observation of the polar magnetic field of the Sun with SO/PHI-HRT

First Name: Daniele
Last Name: Calchetti
Email Address: calchetti@mps.mpg.de
Affiliation: MPS

All Authors: D. Calchetti, S. Solanki, J. Hirzberger, G. Valori, D. Orozco, J. Blanco, T. Oba, H. Strecker, A. Ulyanov

Abstract: Direct remote-sensing observations of the solar poles have been hindered by the restricted view obtained from the ecliptic plane. For the first time ever, Solar Orbiter with its remote-sensing instruments observed the poles of the Sun from out of the ecliptic in the Spring of 2025. Here we report the first measurements of the magnetic field of the solar poles taken when Solar Orbiter was at heliographic latitudes ranging between 14.9 and 16.7 degree. The data-sets were collected by the High Resolution Telescope of the Polarimetric and Helioseismic Imager (SO/PHI-HRT) on board Solar Orbiter. Two sets of observations, approximately one month apart, for the south and north pole are considered in this work. The magnetic flux and flux density measured during these campaigns are reported as a function of the heliographic latitude observed by HRT. The net fluxes show a different latitudinal distribution for the two polar caps. We also discuss the observed dependence of the measured fluxes on the viewing angle. In addition, the north pole high resolution data acquired in October 2025 will be briefly presented and commented.

Speaker: Daniele Calchetti (Max Planck Institute for Solar System Research)

SOW10calchetti.pdf

22 Comparison of Predicted Solar Polar Fields with Solar Orbiter Observations

First Name: Jon
Last Name: Linker
Email Address: linkerj@predsci.com
Affiliation: Predictive Science Inc.

All Authors: Cooper Downs, Ronald Caplan, James Turtle, Pete Riley, Gherardo Valori, Solar Orbiter PHI Team

Abstract: The photospheric magnetic field originating from the poles of the Sun expands into the upper solar atmosphere and out into the solar wind. It can profoundly affect the topology and structure of the entire coronal magnetic field, and, particularly at solar minimum, contributes disproportionately to the open magnetic flux. It is difficult to accurately measure the polar magnetic field from the ecliptic plane, where, until recently, all observations have been made. Surface Flux Transport (SFT) models incorporate the processes by which magnetic flux is transported and dispersed across the solar surface. They can assimilate magnetograms and predict the flux on unobserved portions of the Sun, including the poles. Global maps of the solar magnetic field from SFTs are frequently used in lieu of standard synoptic maps, in part because they predict the polar values. In the past year, Solar Orbiter ascended to nearly 17 degrees heliographic latitude, allowing unprecedented measurements of the solar polar magnetic field by the PHI instrument. We employ the Open-Source Flux Transport (OFT) model to assimilate HMI line-of-sight (LOS) and HMI vector measurements and simulate the surface flux of the Sun over many years. We compare the polar magnetic flux predicted by the model for different realizations around the time period of the polar passes with the PHI measurements. Work supported by NASA and NSF.

Speaker: Jon Linker (Predictive Science Inc.)

23 Full-disk polar magnetic field maps registered with SO/PHI-FDT

First Name: Artem
Last Name: Ulyanov
Email Address: ulyanov@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research

All Authors: Artem Ulyanov, Sami Solanki, Daniele Calchetti, Johann Hirzberger, Hanna Strecker, Gherardo Valori, and David Orozco Suárez

Abstract: The properties of the polar magnetic flux represent one of the missing elements shaping our understanding of how the Sun's magnetic field is generated and transported on global scales. In the pre-Solar Orbiter era, observations of polar fields made from the Earth's perspective were limited by the low signal-to-noise ratio. As a result, integration of numerous measurements, either in space or time, was needed, smearing the overall resolution. This, in turn, inevitably affected how well existing theoretical models could reproduce the observations. The Solar Orbiter's orbit provides a unique opportunity to observe the solar magnetic field in full coverage and resolution. We took advantage of the SO/PHI-FDT instrument capabilities to recover the nearly full-Sun picture of the photospheric magnetic field distribution during the first out-of-ecliptic campaigns in spring and autumn 2025. Our preliminary analysis shows that the polar regions are dominated by unipolar magnetic elements with a mean unsigned value of around 2G. We also report that the distribution of magnetic flux with latitude is seemingly flat above 60 degrees, in contrast to previous studies. We are looking forward to the upcoming high-latitude campaigns to be able to trace the evolution of polar fields throughout the solar cycle.

Speaker: Artem Ulyanov (Max Planck Institute for Solar System Research)

24 online – The Solar Polar-orbit Observatory (SPO) mission

First Name: Hui
Last Name: Tian
Email Address: huitian@pku.edu.cn
Affiliation: Peking University

All Authors: Hui Tian, Yuanyong Deng

Abstract: The polar regions of the Sun remain among the least-explored territories in solar physics, yet they play a crucial role in driving the solar magnetic cycle, generating the fast solar wind, and shaping space weather throughout the heliosphere. Limited by the Earth’s position in the ecliptic plane, past missions have only provided oblique views of the poles, leaving their behavior and evolution poorly understood. This observation gap has left three top-level scientific questions unanswered: How does the solar dynamo work and drive the solar magnetic cycle? What drives the fast solar wind? How do space weather processes globally originate from the Sun and propagate throughout the solar system? The Solar Polar-orbit Observatory (SPO), scheduled for launch in January 2029, aims to address this gap by achieving the first direct imaging observation of the Sun’s poles from high heliolatitudes. Using multiple Earth flybys and a Jupiter gravity assist, SPO will reach an orbital inclination of up to 75° (80° in an extended mission), with a 15-year lifetime (including the 8-year extended mission) covering an entire solar cycle. In order to achieve its scientific goals, SPO will carry a suite of remote-sensing and in-situ instruments to measure the vector magnetic fields and Doppler velocity fields in the photosphere, to observe the Sun in the extreme ultraviolet and X-ray wavelengths, to image the corona and the heliosphere up to 45 solar radii, and to perform in-situ detection of magnetic fields and charged particles in the solar wind. The mission’s vantage point will allow extended observation periods above ±55° latitude, including during the next solar maximum around 2035, when a polar magnetic field reversal is expected. By directly imaging the poles, SPO will provide invaluable insights, revolutionizing our understanding of the Sun and the space weather processes.

Speaker: Hui Tian (Peking University)

Conference Photo

Coffee and Poster A

Coronal structure and dynamics

25 Coronal structure and dynamics — New insights from Solar Orbiter

First Name: Lakshmi Pradeep
Last Name: Chitta
Email Address: chitta@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research

All Authors: Lakshmi Pradeep Chitta

Abstract: The outer solar atmosphere, the million-Kelvin degree hot corona, is intricately governed by the magnetic field. The diverse magnetic landscape in the solar surface results in an equally diverse and complex coronal features. Magnetic structures in the corona range from ~100 km sized tiny brightenings with lifetimes of at most a few seconds to regions on scales of tens of megameters with minimal temporal variations. Understanding the origin and dynamics of this coronal magnetic field is a central theme of the Solar Orbiter mission. The Polarimetric and Helioseismic Imager and the Extreme Ultraviolet Imager, two of the remote-sensing instruments on board Solar Orbiter, capture surface magnetic structures and coronal features at almost exactly the same high spatial resolution of 200 km. These unprecedented observations are providing new insights into the photosphere-corona connection and are refining our understanding of fundamental processes in the magnetized plasma including reconnection and magnetohydrodynamic waves. I will review the recent progress on coronal structure and dynamics with an emphasis on the open questions and possible future directions.

Speaker: Lakshmi Pradeep Chitta (Max Planck Institute for Solar System Research)

26 Reaching New Heights: SoloHI Observations from Outside the Ecliptic Plane

First Name: Phillip
Last Name: Hess
Email Address: phillip.n.hess2.civ@us.navy.mil
Affiliation: US Naval Research Laboratory

All Authors: Phillip Hess, Robin Colaninno, Angelos Vourlidas, Guillermo Stenborg, Evangelos Paouris, Erika Palmerio, Russell Howard, Eleni Nikou

Abstract: As the Solar Orbiter spacecraft moves out of the ecliptic plane, remote sensing observations are becoming available from vantages never before possible. In particular, the imaging of the inner heliosphere from an off-ecliptic angle adds important constraints on the 3D geometry of solar transients and their interplay with the large-scale background wind. This type of imaging makes a crucial step forward for both research and space weather purposes. It also introduces new challenges in properly projecting and co-aliging the images, especially from an off-disk imager like the Solar Orbiter Heliospheric Imager (SoloHI. With an ever-changing roll angle of the spacecraft with respect to the ecliptic, as well as projections along significantly different lines of sight than previous heliospheric imagers, a careful handling of the image plane of the instrument is necessary for properly understanding these images and comparing them with other remote sensing observations in the ecliptic plane. We present the images from the first Solar Orbiter passes at latitudes up to +/- 17°, and introduce methodologies for determining the location of structures within the images in a way that allows for the accurate understanding of the 3D geometries of observed features. The SoloHI images offer exciting new perspectives of the heliospheric current sheet (HCS), solar wind outflows, coronal mass ejections (CMEs), and even the stable dust corona around the Sun, as well as higher resolution over the polar region in the heliosphere than anything that has ever been possible.

Speaker: Phillip Hess (US Naval Research Laboratory)

27 Thermal non-equilibrium cycles in pseudo-streamers

First Name: Clara
Last Name: Froment
Email Address: clara.froment@cnrs-orleans.fr
Affiliation: LPC2E/CNRS

All Authors: Clara Froment and Sophie Masson

Abstract: We report the detection of thermal non-equilibrium (TNE) cycles in a pseudo-streamer observed with SDO/AIA. TNE is an ubiquitous mechanism in the solar atmosphere, especially in coronal loops. These evaporation and condensation cycles are induced by a quasi-steady stratified heating. Long-period EUV pulsations and coronal rain are two manifestations of TNE. There are recent reports of coronal rain at open-closed boundaries such a fan-spine topologies and pseudo-streamers. However, no definite conclusions were drawn on the physical mechanisms driving the coronal rain events. The event we study here has all the characteristics of previous TNE events reported in coronal loops: periodic EUV pulses appearing sequentially in the different channels, according to their peak temperature response order and coronal rain showers by the end of the cooling phases. We further show that the TNE cycles occur both in the closed and in the open field of the pseudo-streamer. Our observations support the findings of recent numerical works showing that TNE can also occur in open field and at open-closed boundaries. In parallel, interchange reconnection occurs gradually all along the open-closed boundary as seen in EUV and with a PFSS modeling. This observation opens further perspectives for the understanding of TNE in the solar atmosphere and its potential implication for the solar wind. Indeed, TNE could also inject mass and energy into the solar wind by its interplay with interchange reconnection.

Speaker: Clara Froment (LPC2E/CNRS)

12:35 Lunch

Coronal structure and dynamics

28 Scaling laws of coronal loops for a 3D MHD loop model driven self-consistently by magnetoconvection

First Name: Cosima
Last Name: Breu
Email Address: brecosima.breu@uni-graz.at
Affiliation: University of Graz

All Authors: Cosima Breu

Abstract: A large part of the solar -and possibly stellar- corona is made up of closed magnetic loops containing hot and bright plasma. The exact physical mechanism leading to the heating of the plasma is still unclear. Numerous scaling laws have been proposed that relate loop properties such as peak temperature, density, or heating rate to coronal loop length and magnetic field. These scaling laws are valuable tools to constrain the mechanism responsible for coronal heating. This is especially true for stars other than the Sun, where the small-scale structure of the corona cannot directly be observed and the interpretation of observations must rely on scaling laws. These scaling relations for coronal loops are usually derived from analytical or numerical models under simplifying assumptions, such as hydrostatic equilibrium or, in the case of simulations, a prescribed driver injecting energy by tangling the magnetic field. In this study, we investigate how loop length and coronal magnetic field strengths influence the energy injection into coronal loops in models driven self-consistently by magnetoconvection rather than by an imposed driver. We model the coronal loop as a straightened magnetic flux tube in a Cartesian box using the radiative 3D MHD code MURaM. The loop is rooted in a shallow convection zone layer at each footpoint, allowing for a self-consistent coupling between the photosphere, chromosphere, and corona. This setup allows for easily controlling the loop length and magnetic field strength while capturing the energy transport through different atmospheric layers. In this talk, I will review existing relations and compare them with new results for loop simulations spanning from the convection zone into the corona.

Speaker: Cosima Breu (University of Graz)

29 Linking Solar Orbiter observations with MURaM simulations of decayless kink oscillations

First Name: Sudip
Last Name: Mandal
Email Address: mandals@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research, Germany

All Authors: Sudip Mandal, Hardi Peter, Cosima Breu, Lakshmi Pradeep Chitta, Patrick Antolin, Sami K Solanki, and the EUI team

Abstract: Decayless kink oscillations are ubiquitous in solar loops. Since these oscillations do not exhibit the typical signs of decay often observed in kink oscillations driven by transient events, it is essential to identify the drivers or mechanisms powering these waves. Several candidates have been proposed, but conclusive evidence for any of them has yet to be identified. In this talk, I will present the evidence, or lack thereof, regarding the postulated wave drivers, based on high-resolution observations obtained from the Solar Orbiter spacecraft. Combining Solar Orbiter data with Atmospheric Imaging Assembly (AIA) images, I will provide a stereoscopic perspective on these oscillations, revealing a new aspect of this phenomenon. Furthermore, I will discuss how these findings compare with the results obtained from a 3D magnetohydrodynamic (MHD) self-consistent simulation of a coronal loop using MURaM. This comparison shows the necessity to identify atypical proxies, such as the wave polarization properties, that shed light on the characteristics of wave drivers and improve our understanding of the phenomena involved.

Speaker: Sudip Mandal (Max Planck Institute for Solar System Research)

30 Does a Coronal Dimming Event Transform the Quiet Sun into a Region with Physical Properties of a Coronal Hole?

"Coronal dimmings, also called transient coronal holes, are well documented following eruptions (e.g. Veronig et al. 2025). Between 17 and 18 March 2022, a coordinated Solar Orbiter–Hinode–IRIS campaign monitored the formation of a coronal dimming following a filament eruption (Ngampoopun et al. 2023).
We investigate whether the eruption produced a coronal-hole-like behaviour in the initially quiet Sun by analysing the chromospheric and coronal response prior and during the dimming.
In SDO/AIA 193 Å images we found, close to the dimming-quiet Sun boundary, a factor of 1.6 ± 0.2 times more EUV brightenings compared to the number of brightenings in the same area prior to the eruption. Such an increase was not observed in SDO/AIA 171 Å and Solo/HRI 174 Å, giving a temperature constraint. Existing bright points appeared relatively unaffected by the change in the magnetic environment. The coronal spectroscopic data of the dimming have converged towards typical coronal hole values: the Doppler velocities changed from 0 to -3 km/s (upflow) and the intensity ratio Si X/S X decreased from 2.1 to 1.4. The chromospheric Mg II emission remained indistinguishable from quiet Sun.
We suggest that the interaction with the open fields of the dimming occurred mainly at higher altitudes than the bright points, and that interchange reconnection at the dimming boundary produced brightenings at 193 Å."

Speaker: Adriana De-Sassi (ETH Zürich)

Session5_De-Sassi.pdf

31 Periodic and small-scale impulsive EUV emission enhancements along network loops

First Name: Antoine
Last Name: Dolliou
Email Address: dolliou@mps.mpg.de
Affiliation: MPS

All Authors: H. Peter, S. Mandal, P. Chitta, L. Teriaca, Y. Chen, D. Calchetti

Abstract: Network loops are a common feature in the quiet Sun, and the processes sustaining their energy budget are still not fully understood. In this work, our aim is to find signatures of the heating processes at the smallest scales, from the photospheric magnetic footpoints of the loop to its EUV emission in the coronal part. We relied on a multi-instrumental (Solar Orbiter/EUI, Solar Orbiter/PHI, IRIS) six-hour long observation of a quiet Sun region to investigate small-scale impulsive EUV emission enhancements with EUI/HRIEUV in three network loops. We measured periodicities between two to four minutes on the coronal part of the loop. In six of the events, plane of sky velocities on EUV perturbations showed fast (> 200 km/s) components; and two of them had a co-temporal slower component (< 80 km/s). In one case, we found that the slower component was associated with plasma motions, as evident from a Doppler shift of -30 km/s in the Si IV line. Signatures of bi-directional flows could also be found in the Si IV line along with the PoS velocities measured in HRIEUV images. Finally, we found evidence of small-scale (8E16 Mx) mixed polarity field emergence and fluctuation near one of the loop footpoints. We concluded that the fast components on the plane-of-sky are consistent with a thermal transfer or plasma flows, while the slower component is consistent with plasma flows. Our observational results shed new light on the driving of these small network loops. In particular, these observations suggest that the physical origin for these network loop brightenings might be found in periodic magnetic reconnection driven by either photospheric motions of the loop footpoints or the reconnection of the loop with other small-scale magnetic bipoles.

Speaker: Antoine Dolliou (Max Planck Institute for Solar System Research)

Session5_Dolliou.pptx

32 Origin and Atmospheric Coupling of Small-scale Solar Transients

First Name: Tanmoy
Last Name: Samanta
Email Address: tanmoy.samanta@iiap.res.in
Affiliation: Indian Institute of Astrophysics, Bangalore, India

All Authors: Tanmoy Samanta

Abstract: Small-scale transients, including spicules, jets, and localized brightenings, are increasingly recognized as important contributors to mass and energy transport between the chromosphere and corona. Recent advances in high-resolution solar observations now enable coherent, multi-layer investigations of their origin, evolution, and coupling across different regions of the solar atmosphere. High-resolution observations from ground-based facilities, such as the 1.6-m Goode Solar Telescope, together with space-based measurements from Solar Orbiter, IRIS, and SDO, demonstrate that many chromospheric transients exhibit clear coronal signatures, indicating strong coupling across atmospheric layers. In this presentation, I will discuss the origin of selected small-scale transients in the lower solar atmosphere, including spicules, jets, and small brightening events, and examine their relevance to heating and dynamics in the upper solar atmosphere and beyond. I will highlight the importance of simultaneous, multi-layer observations extending from the chromosphere to the corona, including spectroscopic diagnostics from Aditya-L1/VELC, for advancing a comprehensive physical understanding of chromosphere–corona coupling.

Speaker: Tanmoy Samanta (Indian Institute of Astrophysics)

33 Exploring coronal dynamics at high temporal and spatial resolution with Metis

First Name: Vincenzo
Last Name: Andretta
Email Address: vincenzo.andretta@inaf.it
Affiliation: INAF - Capodimonte Astronomical Observatory, Naples

All Authors: Marco Romoli and the Metis Team

Abstract: The Metis coronagraph on board Solar Orbiter is providing a new window into coronal dynamics through observations with exceptional temporal and spatial resolution. Its high cadence capabilities (down to 20 s for extended runs) are being utilized to study the extended solar corona from 1.7 to 3.6 solar radii. The spatial resolution at perihelion (2000 km per pixel) also matches the best coronagraphic images available to date. Since the start of the Nominal Science Phase in 2022, these combined capabilities have opened a new window on coronal dynamics. The resulting observations have revealed a range of previously unexplored transient and dynamical phenomena. Results include the detection of density fluctuations with characteristic periods in the 3-5 minute range. Furthermore, high-cadence images have allowed for the characterization of small-scale flows in the middle corona, observed in both the context of transient events like CMEs and in more quiescent regions. We present an overview of these and other results, emphasizing the power of coordinated observations with other Solar Orbiter instruments (such as EUI, SPICE, and the in-situ suite) to link coronal dynamics to their source regions and the nascent solar wind.

Speaker: Vincenzo Andretta (INAF - Capodimonte Astronomical Observatory)

Metis_SOW26_CoronalDynamics_Mac.pdf

Coffee and Poster A

Coronal structure and dynamics

34 Coordinated observations of Metis, EUI/Solar Orbiter and ASPIICS/PROBA3: large scale coronal structures

First Name: Lucia
Last Name: Abbo
Email Address: lucia.abbo@inaf.it
Affiliation: INAF - Astrophysical Observatory of Turin

All Authors: Lucia Abbo, Emanuele Amato, Vincenzo Andretta, David Berghmans, Riccardo Chiartano, Laurent Dolla, Silvano Fineschi, Alessandro Liberatore, Marilena Mierla, Marco Romoli, Daniele Spadaro, Roberto Susino, Luca Zangrilli, Joe Zender, Andrei Zhukov

Titel of your presentation: Coordinated observations of Metis, EUI/Solar Orbiter and ASPIICS/PROBA3: large scale coronal structures

Abstract: We present the first preliminary results of the coordinated observations of Metis, EUI/Solar Orbiter and ASPIICS/PROBA3 acquired in August and October 2025, during the superior and inferior conjunctions between Solar Orbiter and the Earth. These data-sets are crucial for the study of the large scale structure and dynamics of the corona from the limb (@1.1 Rsun) up to 7 solar radia with a continuous coverage of the field of view.

Speaker: Lucia Abbo (INAF - Astrophysical Observatory of Turin)

Abbo_et_al_coord_obs_metis_ASPIICS.pdf

35 Investigating Solar Wind and SEP Formation Using Solar Orbiter Capabilities and Coronal Modeling

First Name: Samantha
Last Name: Wallace
Email Address: samantha.wallace@erau.edu
Affiliation: Embry-Riddle Aeronautical University

All Authors: Samantha Wallace, Natalia Zambrana Prado, Nicholeen M. Viall, Peter Young, Therese A. Kucera, Susan T. Lepri, Stephanie L. Yardley, Vincenzo Andretta, David Lario, Spiro Antiochos, Charles N. Arge, Samuel J. Schonfeld, Carl J. Henney

Abstract: In this work, we leverage multiple Solar Orbiter (SO) capabilities and coronal modeling to investigate the origins and formation of the solar wind and SEPs. We focus on a 6-day interval (2022 March 4–9) when SO was radially aligned with Earth, characterizing mesoscale solar wind structures observed in SO/HIS Fe/O and O⁷⁺/O⁶⁺ ratios and confirming their survival to L1. We use the ADAPT-WSA model to characterize the solar wind sources (e.g., S-web origin), and to relate the Fe/O observed at SO/HIS, with S/O abundances derived by SO/SPICE. We find that solar wind originating from only one of the four SPICE rasters can be interpreted as plasma originating from open fields. The solar wind from the other three require a different interpretation, and we suggest interchange reconnection as the most natural solution. We close with highlighting recent work which uses the same modeling approach to identify the sources of mesoscale downflows observed by SO/METIS at high latitudes, and of widespread SEP events observed at multiple spacecraft. We compare results with and without the inclusion of far-side SO/PHI data to drive WSA, and demonstrate that far-side data assimilation is necessary to accurately derive the global S-web topology and magnetic connectivity, highlighting the need for global photospheric field coverage.

Speaker: Samantha Wallace (Embry-Riddle Aeronautical University)

36 The Multi-slit Solar Explorer (MUSE)

First Name: Bart
Last Name: De Pontieu
Email Address: bdp@lmsal.com
Affiliation: LMSAL

All Authors: Bart De Pontieu, Mark Cheung, Juan Martinez-Sykora, Paola Testa, Amy Winebarger and the MUSE team

Abstract: In this talk I will discuss the upcoming Multi-slit Solar Explorer (MUSE) mission, which is scheduled for launch in 2027. MUSE is a NASA MIDEX mission, composed of a multi-slit EUV spectrograph (in three narrow spectral bands centered around 171Å, 284Å, and 108Å) and an EUV context imager (in two narrow passbands around 195Å and 304Å). MUSE will provide spectral and imaging diagnostics of the solar corona at high spatial (~0.5 arcseconds), and temporal resolution (down to ~0.5 seconds) thanks to its innovative multi-slit design. By obtaining spectra in 4 bright EUV lines (Fe IX 171Å, Fe XV 284Å, Fe XIX-XXI 108Å) covering a wide range of transition region and coronal temperatures along 35 slits simultaneously, MUSE will be able to ``freeze" (at a cadence as short as 10 seconds) with a spectroscopic raster the evolution of the dynamic coronal plasma over a wide range of scales: from the spatial scales on which energy is released (<0.5 arcsec) to the large-scale often active-region size (~ 170 arcsec x 170 arcsec) atmospheric response. I will provide an update on the status of MUSE including numerical simulations illustrating how MUSE observations can help address outstanding questions regarding coronal heating, flares and CMEs. I will also describe the multi-slit data approach and the data products that the MUSE team will provide.

Speaker: Bart De Pontieu (LMSAL)

Solar eruptive events (Flares, CMEs, energetic phenomena)

37 online - Solar Flares observed from the Solar Ultraviolet Imaging Telescope

First Name: Soumya
Last Name: Roy
Email Address: soumyaroy@iucaa.in
Affiliation: Physical Research Laboratory, Ahmedabad, Gujarat, India

All Authors: Soumya Roy

Abstract: Solar flares are among the most energetic phenomena in the solar atmosphere, releasing vast amounts of energy that drive dynamic changes across multiple layers. Understanding their impact on the lower solar atmosphere is critical for modelling energy transport and atmospheric coupling. We present the near-ultraviolet observations of solar flares using the Solar Ultraviolet Imaging Telescope (SUIT) onboard Aditya-L1, focusing on flare signatures in the chromosphere and transition region. SUIT provides full-disk imaging in multiple narrowband UV filters spanning 200–400 nm, enabling simultaneous monitoring of different atmospheric layers of the Sun. We observed the flares in the Mg window and its wings, as well as the continuum across the Balmer jump with two narrowband and one broadband filters. These filters together probe the upper photosphere and lower chromopsheric heights driven by the precipitation during a flare, constraining the physical processes in the impulsive phase of the flare. The signatures observed complement high-energy diagnostics from other instruments, offering a multi-layered view of flare dynamics. These first results demonstrate SUIT’s unique capability to capture chromospheric and transition region responses during flares, providing critical insights into energy coupling between atmospheric layers and pave the way for improved flare modelling.

Speaker: Soumya Roy (Physical Research Laboratory, India)

38 Ultraviolet Irradiance Enhancements and Nonthermal Heating in Flare-associated Eruptions:

First Name: Luke
Last Name: Majury
Email Address: lmajury01@qub.ac.uk
Affiliation: Queen's University Belfast

All Authors: Luke Majury, Marie Dominique, Ryan Milligan, Dana-Camelia Talpeanu, Ingolf Dammasch, David Berghmans

Abstract: While the majority of large magnitude flares (GOES M-class and above) are associated with eruptions of material, the excess irradiance from this material has yet to be quantified. We analyse a sample of ten eruptive M- and X-class flares observed during 2024 and 2025, employing a masking technique to separate the irradiance enhancements from eruption and ribbon sources as observed by SDO/AIA. For four of these events, imaging analysis of HXR data from SolO/STIX and ASO-S/HXI was performed to assess the importance of nonthermal particle heating within the eruptions. The sample-averaged percentages of excess radiated energy by erupted material over the flares' impulsive phases were 10%, 24%, 21% and 13% for the 131 Å, 171 Å, 304 Å and 1600 Å channels, respectively. We find that these eruptions did not show ubiquitous signatures of nonthermal heating, lacking consistent spatial overlap between HXR sources and the erupted material. One event was jointly observed at the solar limb by HXI and STIX at ~170 degrees of separation, with HXR spectroscopy providing insights into differences in nonthermal electron properties at varying atmospheric heights. The observed irradiance contributions from eruptions likely drive spectral variability that may be misinterpreted as signatures of chromospheric evaporation and successful CMEs, particularly in Sun-as-a-star and stellar observations. Further analysis of spatially resolved spectral data from existing instruments such as IRIS and Hinode/EIS, and upcoming instruments such as MUSE and SOLAR-C, may elucidate the role of eruptions in this spectral variability. Additionally, such data may clarify whether turbulent energy release, inferred through nonthermal line broadening, can drive the observed irradiance enhancements.

Speaker: Luke Majury (Queen's University Belfast)

majury_presentation_170326.pptx

Poster A

All these posters will be up on throughout both Monday and Tuesday, during both coffee breaks and the dedicated evening poster sessions.

Wednesday 18 March

Solar eruptive events (Flares, CMEs, energetic phenomena)

39 On the Statistics of Coronal Mass Ejections

First Name: Marilena
Last Name: Mierla
Email Address: marilena.mierla@oma.be
Affiliation: Royal Observatory of Belgium

All Authors: EUI consortium team

Abstract: Coronal mass ejections (CMEs) are huge eruptions of magnetized plasma that propagates out from the Sun into space. These powerful and complex events can interact with Earth's magnetic field and cause important disruptions. Because of their impact, scientists study CMEs to understand where they start, how they erupt, and how they travel from the Sun into interplanetary space. In my presentation, I will share a statistical overview of the properties of CMEs and update you on recent research using data from the Solar Orbiter spacecraft. I will also talk about the challenges scientists face when studying CMEs and the opportunities for future discoveries with new space missions.

Speaker: Marilena Mierla (Royal Observatory of Belgium)

Session6_Mierla.pdf

40 Disruption of the October 3, 2024 CME by the Heliospheric Current Sheet – A Sun-to-Earth Analysis

First Name: Manuela
Last Name: Temmer
Email Address: manuela.temmer@uni-graz.at
Affiliation: Institute of Physics, University of Graz, Austria

All Authors: M. Temmer(1), S.G. Heinemann (1,2), N. Dresing (3), E.

Abstract: We investigate combined remote-sensing and in-situ data for a case study on a coronal mass ejection (CME) interacting with the nearby located heliospheric current sheet (HCS). The CME is related to the largest flare (X9.0) of solar cycle 25 on October 3, 2024. We find the CME source region to be a so-called nested active region, hence, persisting over several solar rotations. The active region and its evolution is therefore significantly linked to the structure of the global magnetic field. In-situ measurements indicate that a combined system of HCS and CME structures is propagating outward and generating a weak shock front ahead of it. The CME itself is highly interrupted by clear HCS-related structures, i.e., the heliospheric plasma sheet (HPS). The interaction process caused the CME-related shock-sheath region to be separated from the magnetic ejecta part by almost 40 hours. This event shows the intrinsic relation between solar surface structures, global magnetic field and the evolution of complex eruptive events.

Speaker: Manuela Temmer (Institute of Physics, University of Graz, Austria)

41 Global MHD Modelling of CME Evolution as Context for Multi-Spacecraft Observations

First Name: Erika
Last Name: Palmerio
Email Address: epalmerio@predsci.com
Affiliation: Predictive Science Inc.

All Authors: Erika Palmerio, Cooper Downs, Ronald M. Caplan, Phillip Hess, Robin C. Colaninno, Abril Sahade, Cecilia Mac Cormack

Abstract: Coronal mass ejections (CMEs) have traditionally been investigated through two distinct observational regimes: in the solar corona through remote-sensing imagery and in interplanetary space through in-situ measurements. Since the launches of Parker Solar Probe in 2018 and Solar Orbiter in 2020, this long-standing division has become increasingly blurred. Parker Solar Probe has recorded several CMEs in situ within the corona while simultaneously imaging the surrounding environment, whereas Solar Orbiter has begun delivering the first high-resolution views of the inner heliosphere from inside 1 au—and more recently from out of the ecliptic plane. These instruments provide unprecedented views of the corona and inner heliosphere, capturing CME evolution at different stages from their eruption through their interplanetary journey. At the same time, the growing fleet of heliophysics missions increases the likelihood of multi-spacecraft observations of individual CME events, but also introduces new challenges in synthesising diverse measurements across platforms, distances, and vantage points. To address these challenges, we employ global magnetohydrodynamic (MHD) simulations with the CORHEL model to provide physical context for interpreting complex, multi-modal, and multi-spacecraft observations. These simulations allow CMEs to be followed self-consistently from their solar initiation through their heliospheric evolution, filling observational gaps and enabling direct comparisons with both remote-sensing and in-situ signatures. Beyond the advantages of analysing full 3D distributions of magnetic field and plasma parameters, an important component of our approach is the generation of synthetic observables designed to mimic real measurements. These include synthetic EUV/X-ray emission, white-light coronagraph/heliospheric imaging, and in situ time series that replicate the fields of view and data characteristics of existing instruments. We demonstrate how such simulation-based observables, combined with global MHD modelling, help disentangle line-of-sight effects, connect remote-sensing and in-situ signatures, and provide a unified context for interpreting multi-spacecraft observations of CMEs throughout the corona and inner heliosphere.

Speaker: Erika Palmerio (Predictive Science Inc.)

42 How Solar Flares Look from Solar Orbiter: X-ray Insights from Half a Solar Cycle of Observations

First Name: Laura
Last Name: Hayes
Email Address: laura.hayes@dias.ie
Affiliation: Dublin Institute for Advanced Studies

All Authors: Laura Hayes, Säm Krucker, Shane Maloney, Hannah Collier

Abstract: Solar Orbiter has now observed half a solar cycle of solar activity, with STIX providing a uniquely rich hard X-ray view of flares from a wide range of distances and heliospheric vantage points. From close-approach disk flares to far-limb and backside events, STIX has built the largest and most diverse X-ray flare dataset of Solar Cycle 25, allowing us to ask: what does a “typical” solar flare look like from Solar Orbiter? Using the full STIX flare list and a superposed epoch analysis, we identify new, recurring patterns in the timescales of energy release, the evolution of impulsive hard X-ray signatures, and statistical relationships between duration, spectral behaviour, pulse structure, and other flare properties. These results establish a robust X-ray flare baseline that can be compared with complementary flare diagnostics, enabling multi-perspective studies of flare evolution. We also highlight several of the largest and most complex events, showing how extended, multi-pulse hard X-ray emission fits within the broader statistical trends. Together, these findings provide new constraints on particle acceleration, magnetic reconnection, and CME initiation, offering fresh mission-scale insight into eruptive solar activity.

Speaker: Laura Hayes (Dublin Institute for Advanced Studies)

43 Unsaturated EUV imaging of solar flares at unprecedented temporal/spatial resolution

First Name: David
Last Name: Berghmans
Email Address: david.berghmans@oma.be
Affiliation: Royal Observatory of Belgium

All Authors: David Berghmans, Hannah Collier, Marie Dominique, Laua Hayes, Jana Kasparova, Emil Kraaikamp, Graham Kerr, Juraj Lorincik, Konstantina Loumou, Hamish Reid, Daniel Ryan, Cis Verbeeck

Abstract: Imaging flares in the EUV is difficult as the flare brightness easily exceeds the sensor dynamic range. This leads to local saturation and blooming. Also, flare dynamics are usually not resolved, even at the resolution of AIA. The HRIEUV telescope of the EUI instrument onboard Solar Orbiter has surpassed these limitations. Blooming of the flare signal is avoided as HRIEUV uses a CMOS sensor and not a CCD. Saturation is avoided by operating the instrument in a cycle in which the regular images are interleaved by a large number of short exposure images. The explosion of telemetry is avoided by advanced compression that allocates autonomously the limited bits to describe the best exposed features in the image, which is the flare, wasting very little bits on the rest of the underexposed data. We present an overview of the numerous results obtained from observations of a few tens of C and M flares, down to 100km & 2s scales, that have been coordinated through the so-called Major Flare Watch SOOPs with SPICE, PHI/HRT and STIX. This includes previously unresolved dynamics in footpoints and ribbons with bright plasma blobs raining down, persistent bidirectional flows near the flare core, and overall unwinding structures. We will conclude with the relevance of these observations for future flare observations such as on the SPARK mission proposed for the ESA M8 mission call.

Speaker: David Berghmans (GNOI)

20260318-SolarOrbiterWorkshop-Berlin-UnsaturatedEUVimagingFlares_small.key.pdf

Coffee and Poster B

Solar eruptive events (Flares, CMEs, energetic phenomena)

44 Energy release in solar flares

First Name: Vanessa
Last Name: Polito
Email Address: polito@lmsal.com
Affiliation: Lockheed Martin Solar & Astrophysics Laboratory

All Authors: Vanessa Polito

Abstract: In this review talk, I will discuss recent advances in our understanding of the energy-release mechanisms operating during the impulsive phase of solar flares. Although the fundamental picture of magnetic reconnection as the driver of flare energy release is well established, many key details of how this energy is converted into various forms, and how it is transported through the solar atmosphere, remain poorly understood. I will highlight recent discoveries enabled by high-resolution imaging and spectroscopic observations from IRIS, Solar Orbiter, and Aditya, which provide unprecedented views of the fine-scale dynamics in the chromosphere, transition region, and corona during flares. By combining these observations with advanced numerical simulations and theoretical models, we can now place significantly stronger constraints on the physical processes governing the release, transport, and deposition of energy that ultimately drive solar flares.

Speaker: Vanessa Polito (Lockheed Martin Solar & Astrophysics Laboratory)

45 Spatial Variation of Flare Energy Transport Mechanisms as Revealed by Solar Orbiter's Major Flare Campaign

First Name: Graham
Last Name: Kerr
Email Address: graham.kerr.2@glasgow.ac.uk
Affiliation: University of Glasgow

All Authors: Sam Krucker, Joel Allred, Jenny M Rodriguez-Gomez, Andrew Inglis, Daniel Ryan, Laura Hayes, Ryan Milligan, Adam Kowalski, Joesph Plowman, Peter Young, Therese Kucera, Jeffrey Brosius

Abstract: Solar flare ribbons and footpoints represent crucial diagnostic windows onto the various process involved in flare energetics, including reconnection, particle acceleration and plasma dynamics. High-resolution, high-cadence observations have revealed substantial fine-scale structure to those lower atmospheric sources, which undoubtedly impart information about energy release, particle acceleration and transport. Here we present flare-optimised EUI/HRI, STIX and SPICE observations from Solar Orbiter's spring 2024 Major Flare campaign. In particular, we focus on a small event in which SPICE's slit crossed two flare ribbons, providing spectral information from two footpoints. Analysis of the Lyβ and Lyγ lines found that each footpoint responded in a rather different manner. Careful comparisons to state-of-the-art flare radiation hydrodynamics simulations (driven by STIX and EUI derived inputs) revealed that this was due to different energy transport mechanisms dominating in each footpoint, despite being nearby each other. One footpoint was consistent with precipitation of accelerated particles, whereas the other was instead consistent with an enhanced heat flux from a directly heated flare corona. The implication being that electron beams do not dominate energetics in each location along flare ribbons. We conclude by looking ahead to future observations (e.g. MUSE) that could help us understand where, when, and why energy transport mechanisms vary along flare structures.

Speaker: Graham Kerr (University of Glasgow)

SolO_IRIS_Aditya_Feb26_GKerr.pdf

46 Solar Orbiter Observations Take Us Beyond the Standard Solar Model

First Name: Eric
Last Name: Priest
Email Address: eric.r.priest@st-andrews.ac.uk
Affiliation: ST ANDREWS UNIVERSITY

All Authors: ERIC PRIEST and PRADEEP CHITTA

Abstract: We report observations of the pre-flare and impulsive phases for an M7.7 solar flare on Sept 30, 2024 by Solar Orbiter (especially by the Extreme Ultraviolet Imager (EUI) and the Spectrometer/Telescope for Imaging X-rays (STIX)). During the preflare phase, the mild heating comes, as expected, from a region below a rising magnetic flux rope where the magnetic field is slowly reconnecting. However, during the impulsive phase, the hard x-rays are surprisingly associated with a different location. They suggest that the standard flare model needs to be changed to incorporate magnetic reconnection of an entirely different character, in ways that we describe.

Speaker: Eric Priest (ST ANDREWS UNIVERSITY)

12:15 Lunch

Solar eruptive events (Flares, CMEs, energetic phenomena)

47 Magnetic Drivers of Solar Flares

First Name: Maria
Last Name: Kazachenko
Email Address: maria.kazachenko@colorado.edu
Affiliation: University of Colorado Boulder

All Authors: Maria D. Kazachenko

Abstract: Space weather is primarily driven by the activity of our Sun. Invisible yet powerful magnetic fields, generated within the Sun, determine when and where the next solar eruption will occur. In this talk, I will review how recent advances in observations of solar magnetism, data-driven modeling, and novel analysis techniques have allowed us to study flare magnetism in unprecedented detail.

Speaker: Maria Kazachenko (University of Colorado Boulder)

48 Evolution of Flare Ribbon Bead-like Structures in a Solar Flare

First Name: Ryan
Last Name: French
Email Address: ryan.french@lasp.colorado.edu
Affiliation: Laboratory for Atmospheric and Space Physics / University of Colorado Boulder

All Authors: Ryan J. French, Maria D. Kazachenko, David Berghmans, Elke D’Huys, Marie Dominique, Ritesh Patel, Dana-Camelia Talpeanu, Cole A. Tamburri, and Rahul Yadav

Abstract: We present fast cadence and high resolution observations of flare ribbons from the Solar Orbiter Extreme Ultraviolet Imager (EUI). Utilizing the short-exposure observations from the EUI High Resolution Imager in EUV (HRIEUV), we find small-scale blob/bead-like kernel structures propagating within a hook at the end of a flare ribbon, during the impulsive phase of a C9.9-class solar flare. These bead structures are dynamic, with well-resolved spatial separations as low as ~420-840 kilometers (3-6 pixels) – below the observable limit of full-disk solar imagers. We analyze the evolution of the plane-of-sky apparent velocity and separation of the flare ribbon structures, finding evidence for multiple processes occurring simultaneously within the flare ribbon. These processes include – quasi-periodic pulsation (QPP)-like brightenings, slow back-and-forth zig-zag motions along the ribbon, rapid apparent motions along the ribbon (600+ km/s), and stationary blob-like structures. Finally, we conduct Fast Fourier Transform analysis and analyze the start times of exponential growth in the power spectrum at different spatial scales across the flare ribbon. Our analysis reveals that the ribbon beads form with a key spatial separation of 1.7-1.9 Mm, before developing into more complex structures at progressively larger and smaller spatial scales. This observation is consistent with predictions of the tearing mode instability.

Speaker: Ryan French (Laboratory for Atmospheric and Space Physics / University of Colorado Boulder)

49 Constraining ion acceleration in behind-the-limb gamma-ray flares with Fermi-LAT, SolO/STIX, and ground-based radio observations

First Name: Song
Last Name: Tan
Email Address: awarmuth@aip.de
Affiliation: Leibniz-Institute for Astrophysics Potsdam (AIP)

All Authors: Alexander Warmuth, Melissa Pesce-Rollins, NIcola Omodei, Song Tan

Abstract: Compared to energetic electrons in solar flares, which can be readily observed in hard X-rays and radio, our understanding of energetic ions is severely deficient. Our main diagnostics for ions are gamma-ray observations, which remain challenging. A particularly intriguing case are behind-the-limb (BTL) gamma-ray flares, where the flare is occulted as seen from Earth, but nevertheless gamma-ray emission is detected by near-Earth spacecraft. Here, we investigate the relationship between the gamma-ray emission measured with Fermi-LAT, hard X-ray observations from STIX on Solar Orbiter, and ground-based radio observations, for small sample of BTL gamma-ray flares. In all events, type II radio bursts were present that were synchronized in time with the gamma-ray emission. Conversely, we find a significant delay between the impulsive phase of the flare as recorded by STIX and the gamma-ray emission. These findings support the notion that the highly relativistic ions that produce the gamma-rays in BTL flares are accelerated at CME-driven propagating coronal shock waves rather than in large-scale coronal loops.

Speaker: Song Tan (Leibniz-Institute for Astrophysics Potsdam (AIP))

50 Analysis of quasi-periodic pulsations and three-dimensional slipping reconnection using IRIS & STIX

First Name: Juraj
Last Name: Lorincik
Email Address: lorincik@baeri.org
Affiliation: BAERI/LMSAL

All Authors: Juraj Lorincik, Hannah Collier, Vanessa Polito, Laura Hayes, William H. Ashfield IV, Nabil Freij

Abstract: Slipping motions of flare ribbon kernels and the formation of hard X-ray (HXR) footpoints are important observational signatures of magnetic reconnection. The spatio-temporal correspondence between the ribbon ultraviolet and HXR emission, both often quasi-periodic, is however largely unexplored. We focus on high-cadence IRIS and STIX observations of an M9.6-class flare from 2022 March 31. Non-thermal emission captured by STIX exhibited QPPs with periods of about 35 s, stemming from two stationary footpoint sources in the central flare region. Most STIX QPPs were correlated with intensity pulsations captured by the Slit Jaw Imager (SJI) of IRIS in portions of ribbons co-spatial with the HXR footpoints. The Si IV 1402.77 line spectra in one of these regions showed intensity, Doppler speed, and broadening pulsations partially overlapping with the HXR QPPs. Meanwhile, SJI also observed slipping kernel motions elsewhere in the ribbons whose timing, locations, and associated UV intensity variation were difficult to associate with HXR emission. Our analysis suggests prominent quasi-periodic non-thermal energy deposition into a specific loop system near the reconnection site, while the rate of the energy deposition to slipping kernels was likely lower. Our investigation provides a multi-faceted view of 3D magnetic reconnection and its energization of the lower solar flare atmosphere.

Speaker: Juraj Lorincik (BAERI/LMSAL)

Coffee and Poster B

Solar eruptive events (Flares, CMEs, energetic phenomena)

51 Small EUV brightenings in region of high free magnetic energy before a flare - are they a signature of the flare onset?

First Name: Louise
Last Name: Harra
Email Address: louise.harra@pmodwrc.ch
Affiliation: PMOD/WRC & ETH Zurich

All Authors: Louise Harra, Kanya Kusano, Yingjie Zhu, Krzysztof Barczynski, Adriana De Sassi, Ioannis Kontogiannis

Abstract: The Solar Orbiter high resolution EUV imager (HRI_EUV) has observed a number of solar flares with the highest ever spatial resolution in the corona. An observation was made on 19 March 2024 when Solar Orbiter was close to perihelion at a distance of 0.45 A.U. from the Sun. The spatial resolution at this time was 310 km for a 2 pixel resolution. This high resolution allows an analysis of the smallest scale EUV structures before the flare begins. The flare reaches a GOES X-ray classification of M-class. Solar Orbiter was 3.3 degrees separation from the Earth, allowing easy comparison to datasets from other Earth orbiting instruments. It is still difficult to predict when and where exactly a flare will occur, although the flare process itself is well described by the Carmichael-Sturrock-Hirayama-Kopp-Pnueman (CSHKP) magnetic reconnection model. In this work, we compare the observations with an MHD instability model which could be responsible for the trigger of a flare. This is the double-arc instability described by Kusano et al. (2020). They have developed a flare prediction model based on this instability and we compare the locations of small-scale brightenings seen with HRI. There are indications that the largest high free-energy regions are located where small-scale brightenings are observed. These could potentially be used as a proxy of energy available within an active region for flaring.

Speaker: Louise Harra (PMOD/WRC & ETH Zurich)

Session6_Harra.pptx

52 Major advances in solar energetic particle research thanks to Solar Orbiter and Parker Solar Probe missions

First Name: Laura
Last Name: Rodríguez-García
Email Address: lau.rod.gar@gmail.com
Affiliation: European Space Agency

All Authors: Laura Rodríguez-García

Abstract: Solar Orbiter and Parker Solar Probe are providing unprecedented observations of solar energetic particles (SEPs) close to the Sun. Solar Orbiter’s Energetic Particle Detector (EPD) measures SEPs with high temporal and spatial resolution and has revealed key characteristics of SEP events—including onset timing, energy spectra, anisotropies, and composition—at distances down to 0.28 au. These measurements have advanced our understanding of SEP injection, acceleration, and transport processes, and their connections to flares, jets, CMEs, and interplanetary shocks. Solar Orbiter’s unique orbit has enabled multi-spacecraft studies of SEP evolution in the inner heliosphere. Parker Solar Probe reached a record perihelion of 9.8 solar radii in December 2024. Its ISʘIS instrument suite continues to operate in excellent condition, returning data on energetic ions and electrons across a broad energy range. These measurements provide unprecedented views of SEP behavior extremely close to the Sun, particularly as solar activity increased toward the maximum of Solar Cycle 25. Together, the complementary observations from EPD and ISʘIS are offering new insight into how solar eruptions produce and distribute energetic particle radiation throughout the heliosphere. This presentation highlights the most recent and significant results from both missions and their combined contributions to advancing our understanding of SEPs.

Speaker: Laura Rodríguez-García (European Space Agency)

53 The temporal and spatial scales of EUV flare kernels: New insights from EUI/HRI

First Name: Hannah
Last Name: Collier
Email Address: hannah.collier@fhnw.ch
Affiliation: FHNW

All Authors: Hannah Collier, Säm Krucker, Laura Hayes, Emil Kraaikamp, David Berghmans, Daniel Ryan

Abstract: By studying the dynamics of flare ribbons, one obtains an indirect measurement of reconnection in the corona. The aim of this work is to quantify the spatial and temporal scales of EUV flare ribbon kernels as a probe of the spatial extent and duration of energy injection in solar flares. To do this, unprecedented data from the March 2024 major flare campaign of Solar Orbiter were used. These data were obtained at high-cadence in short-exposure mode with the Extreme Ultraviolet Imager's HRI telescope. Individual kernels were automatically identified and from this, the size distributions of kernels for different intensity thresholds were derived. In addition, an average light curve of individual kernels was extracted. Our analysis shows that a significant fraction of kernels were unresolved at a plate scale of 135 km/pix. Furthermore, we derived incredibly short injection times of less than a few seconds. These results emphasise the small spatial and short temporal scales involved in flare energy release. These findings necessitate an in-depth investigation into the implications of such small areas and short injections on the energy flux deposited in solar flares, and the response of the atmosphere.

Speaker: Hannah Collier (FHNW)

Poster B

All these posters will be up on throughout both Wednesday and Thursday, during both coffee breaks and the dedicated evening poster sessions.

Conference Dinner

Google Maps Link

Thursday 19 March

Connecting solar surface and atmosphere with the heliosphere

54 Connecting the structure and dynamics of coronal streamers and the heliospheric plasma sheet

First Name: Alexis
Last Name: Rouillard
Email Address: arouillard@irap.omp.eu
Affiliation: IRAP CNRS FR & AIP DE

All Authors: Alexis P. Rouillard

Abstract: The solar wind extension of solar helmet streamers are the heliospheric current sheet and its plasma sheet. We will review recent research on the structure and dynamics of helmet streamers exploiting the detailed imaging taken by the fleet of spacecraft currently observing the solar atmosphere. Imaging of the large-scale dynamics of helmet streamers and their rays will be compared with local in situ measurements of the plasma sheet in the outer corona and in the solar wind. This will provide new insights on the physical processes operating continually to sustain these dynamical structures. We will discuss the broader implications of these findings for the evolution of the solar magnetic field and the acceleration of particules to high energy.

Speaker: Alexis Rouillard (IRAP CNRS FR & AIP DE)

55 From Sun to Heliosphere: Validating CME Evolution Models with Solar Orbiter

First Name: Abril
Last Name: Sahade
Email Address: abril.sahade@nasa.gov
Affiliation: NASA Goddard Space Flight Center

All Authors: Abril Sahade, Cecilia Mac Cormack, Angelos Vourlidas, Judith Karpen and Teresa Nieves-Chinchilla

Abstract: Coronal mass ejections (CMEs) are major drivers of severe space-weather disturbances, and improving the accuracy of their predictive modeling is essential for effective mitigation strategies. Yet, the complex physics governing CME initiation and evolution, combined with limited observational constraints, continues to hinder reliable forecasting. In this study, we examine how the pre-eruptive magnetic configuration shapes CME evolution and heliospheric propagation. We use physics-based magnetohydrodynamic simulations, covering from the solar surface to 1 au, to analyze the CME that erupted on 26 October 2024. This event, observed both remotely and in situ by multiple spacecraft, including key imaging from Metis and SoloHI and in situ data from Solar Orbiter, provides an excellent opportunity to assess model performance. By varying the initial flux-rope parameters, we evaluate the sensitivity of the modeled CME trajectory, arrival time, and geoeffective impact. Solar Orbiter observations were critical for constraining the CME geometry and identifying the parameter set that yields the best correspondence with the measured evolution. Our results highlight the strong dependence of simulation outcomes on the initial conditions and underscore the importance of multi-perspective observations for improving CME modeling and advancing the reliability of space-weather forecasts.

Speaker: Abril Sahade (NASA Goddard Space Flight Center)

56 High-resolution observations of the slow solar wind sources

First Name: Krzysztof
Last Name: Barczynski
Email Address: krzysztof.barczynski@pmodwrc.ch
Affiliation: PMOD/WRC Davos

All Authors: Krzysztof Barczynski, Louise Harra, Nils Janitzek, David Berghmans, Cis Verbeeck, Andrei Zhukov, Yingjie Zhu, Tania Varesano, Cristina H. Mandrini, Gherardo Valori

Abstract: The origin of the slow solar wind remains an open question. Plasma upflows at active region borders are considered a possible source. The mechanisms driving these upflows are not fully understood, but proposed processes include: magnetic reconnection at different atmospheric layers, magnetoacoustic waves, small-scale heating events and others. We discuss such mechanisms in relation to observed atmospheric features to determine their relative importance. We analysed an upflow region observed on 29 March 2023 using data from Solar Orbiter, IRIS, and Hinode. Spectroscopic observations from Hinode/EIS and IRIS provided Doppler velocity maps spanning from the chromosphere to the corona, allowing the characterization of plasma dynamics in different layers. For the first time, we conducted a detailed temporal-series analysis of processes within upflow regions over a 4-hour period, using coordinated spectroscopic observations from IRIS (48 rasters), EIS (8 rasters), SPICE (500 rasters), and imaging data from EUI/HRI (3300 frames). A diagnostic method combining Doppler velocity map, magnetic field measurements and first ionization potential (FIP) bias was developed to infer the dominant drivers of the observed upflows. High-resolution images from EUI/HRI (Solar Orbiter), IRIS, and SDO/AIA were used to examine the connection between upflow mechanisms and coronal structures. Our results indicate that the strongest upflows originate in the upper transition region and lower corona, where magnetic reconnection between open and closed field lines likely plays a key role, but other mechanisms appear to act together to sustain the observed plasma upflows.

Speaker: Krzysztof Barczynski (PMOD/WRC Davos)

57 Connecting the Solar Corona to the Solar Wind

First Name: Stephanie
Last Name: Yardley
Email Address: steph.yardley@northumbria.ac.uk
Affiliation: Northumbria University

All Authors: Stephanie Yardley

Abstract: One of the main goals of solar and heliospheric physics is to gain a complete picture of the dynamic processes occurring in the solar corona and how these influence the inner heliosphere. Missions such as ESA/NASA's Solar Orbiter, which couples unprecedented, close-up views of the solar atmosphere to solar wind measurements in the inner heliosphere, provide invaluable insights into the sources, release and transport of the solar wind. I will highlight results from Solar Orbiter's first dedicated Fast Wind SOOP campaign in October 2023, connecting microstreams to their coronal sources. I will also present a new connectivity pipeline developed during the ESA Hackathon, which has been used to analyse the March 2025 observations from Solar Orbiter's first latitudinal scan of the southern polar coronal hole, enabled by its recently inclined orbit.

Speaker: Stephanie Yardley (Northumbria University)

58 Propagation of magnetic deflections driven by solar jets: a pathway to switchback formation

First Name: Jade
Last Name: Touresse
Email Address: jade.touresse@lpp.polytechnique.fr
Affiliation: Laboratoire de Physique des Plasmas, Sorbonne Université, CNRS

All Authors: J. Touresse, E. Pariat, C. Froment, V. Aslanyan, P. F. Wyper, L. Seyfritz

Abstract: Parker Solar Probe (PSP) has recently detected widespread localised magnetic deflections in the young solar wind, known as switchbacks. Rarely observed near Earth, these features have spurred investigations into their origin. A prominent theory is that switchbacks originate in the lower corona through magnetic reconnection processes, linked to solar jet activity. Jets are impulsive phenomena, observed at various scales, in different solar atmosphere layers, associated with the release of magnetic twist and helicity. To investigate this, we ran 3D Magnetohydrodynamic (MHD) parametric simulations of solar-jet-like events using the Adaptatively Refined MHD Solver (ARMS) code. Based on the model of Pariat et al. 2009, the simulations explore how variations in the atmospheric plasma β influence jet dynamics and propagation under different coronal and solar wind conditions, including fully sub-Alfvénic regimes and varying Alfvén surfaces. The results reveal that U-loops, prevalent at jet onset, do not propagate in the low-beta corona, preventing full magnetic reversals from reaching the super-Alfvénic wind. Using a simulated PSP trajectory through the magnetic wavefront of the jet, we produced synthetic in-situ velocity and magnetic field data of a switchback along with a 3D visualization of the magnetic geometry. Two distinct field-line configurations were identified, whose evolution depends strongly on the surrounding plasma β. Overall, these results demonstrate that jet-like events can generate and propagate magnetic deflections, shedding light on the possible formation processes of switchbacks.

Speaker: Jade Touresse (Laboratoire de Physique des Plasmas, Sorbonne Université, CNRS)

Coffee and Poster B

Connecting solar surface and atmosphere with the heliosphere

59 Understanding How Small-scale Photospheric Magnetic Fields Influence the Global Solar Corona and Solar Wind

First Name: Cooper
Last Name: Downs
Email Address: cdowns@predsci.com
Affiliation: Predictive Science Inc.

All Authors: Cooper Downs, Caroline L. Evans, Donald Schmit, Jon A. Linker, Viacheslav S. Titov

Abstract: Our march toward increasingly higher-resolution photospheric and coronal measurements has revealed a close connection between low coronal processes and small-scale flux elements at the surface below. At the same time, large field of view observations of the low and middle corona reveal fine-scale plasma structures embedded within the magnetic skeleton of the global corona. Understanding the links between the small-scale photospheric field and the structuring of the global corona has important implications for coronal heating and solar wind formation. In this presentation, we detail our ongoing effort to study this problem from a global perspective, by varying properties of the surface magnetic field inputs to a thermodynamic MHD model of the global solar corona. By incorporating magnetic data at different resolutions—both globally and locally—we find that the magnetic mappings of both closed- and open-field regions within the corona become increasingly fragmented and complex. We show how this fragmented connectivity leads to subtle changes in flux-tube properties at the base of the corona. This provides a means to alter both the local coronal heating rate and thermodynamic properties of coronal flux-tubes, which links to fine-scale structures that can be observed within the extended corona and solar wind. The implications for the dynamical evolution in the corona and heliosphere as a result of driving by the quiet-sun magnetic network are also discussed.

Speaker: Cooper Downs (Predictive Science Inc.)

60 Electrons in the solar wind: connecting the collisional corona with the collisionless heliosphere

First Name: Daniel
Last Name: Verscharen
Email Address: d.verscharen@ucl.ac.uk
Affiliation: University College London

All Authors: Daniel Verscharen, Jingting Liu, Christopher Owen, and Georgios Nicolaou

Abstract: Electrons are a subsonic plasma species in the solar wind. Their kinetic behaviour is - to a much greater extent than the proton behaviour - the result of an interplay between global properties of the Sun-heliosphere system and local plasma processes. The global properties of the heliosphere include the interplanetary electrostatic potential, the large-scale interplanetary magnetic field, and the density profile of the plasma. The local plasma processes include collisions, wave-particle interactions, and turbulence. Through this interplay, the electron distribution function develops interesting kinetic features that are observable in situ with Solar Orbiter's SWA/EAS. The change in the overall collisionality of the electrons from the corona to the solar wind plays a key role for the definition of the relevant kinetic processes depending on distance from the Sun. In addition to a collision-dominated quasi-Maxwellian core, the distribution exhibits suprathermal populations in the form of the strahl and halo components as well as cut-offs due to loss effects in the interplanetary potential. We discuss the processes that shape the electron distribution in the solar wind, the interaction of electrons with local structures such as turbulence, waves, and magnetic holes, and the impacts of these structures on the global electron transport in the heliosphere.

Speaker: Daniel Verscharen (University College London)

61 Evolving Large-Scale Structure of the Corona and Heliosphere: Comparison of SoloHI and Synthetic Observations

First Name: Robin
Last Name: Colaninno
Email Address: robin.c.colaninno.civ@us.navy.mil
Affiliation: US Naval Research Laboratory

All Authors: Robin Colaninno, Philip Hess, Erika Palmerio, Eleni Nikou

Abstract: The transition between the solar corona and inner heliosphere presents a challenge for both physics and nomenclature. Historically, these two regions have been defined by their method of measurement: the solar corona is imaged using remote sensing instruments, while the heliosphere is sampled with in situ. Although the historic differences in measurement methods between the corona and inner heliosphere have been greatly reduced, a physical transition of the plasma environment from magnetically dominated to hydrodynamic occurs between the Sun and 1 AU. Magnetohydrodynamic (MHD) simulations primarily use a height of 20-30 R⊙ as the boundary between the magnetically dominated corona and the hydrodynamic heliosphere. The computational transition between coronal and heliospheric models is critical for propagating information from the solar-driven boundary conditions through the heliosphere to 1 AU through the model. We approach this critical region from a new perspective by combining MHD simulations with images from the Solar Orbiter Heliospheric Imager (SoloHI) to better understand the transition between coronal and heliospheric models. While SoloHI cannot provide direct, quantitative measurements of the plasma, it can be used to validate the shape, magnitude, and frequency of macro-scale transient structures in the solar wind. For this study, we exploit the 2024 April 8 solar eclipse period, known as the Great North American Eclipse, whose path of totality crossed most of the eastern United States. To complement the intensive ground-based observations of the solar corona made possible by the eclipse, extraordinary MHD modeling of the time period was performed. At the time of the eclipse, SoloHI was positioned in the heliosphere 96° East of the Sun-Earth line and looked back towards the Earth. The SoloHI observations provide a side view of this key transition region that has not yet been used to validate the models.

Speaker: Robin Colaninno (US Naval Research Laboratory)

Session#7-Colaninno.pptx

62 The influence of Solar Orbiter/ PHI far-side information on coronal holes and solar wind predictions

First Name: Evangelia
Last Name: Samara
Email Address: evangelia.sam@gmail.com
Affiliation: NASA/GSFC

All Authors: Evangelia Samara, C. Nick Arge, Samuel Schonfeld, Alison Farrish, Carl Henney, Teresa Nieves-Chinchilla

Abstract: In this work we incorporate Solar Orbiter’s Polarimetric and Helioseismic Imager (PHI) Full Disc Telescope (FDT) observations into the Air Force Data Assimilative Photospheric flux Transport (ADAPT) model to construct more complete global solar photospheric maps. We feed these maps into the Wang-Sheeley-Arge (WSA) model to reconstruct the solar corona and perform solar wind simulations for a period of two months in 2024 at multi-spacecraft locations (Solar Orbiter, PSP, ACE, STEREO-A). We assess the quality of our predictions, and compare our results when no FDT data have been employed in order to understand how the addition of far side information affects the open magnetic field topologies on the Sun, their connectivity with various spacecraft of interest, the shape and structure of the heliospheric current sheet, as well as the solar wind predictions at different points in the interplanetary space. Our results demonstrate the value of incorporating far-side information in improving the heliospheric modeling and forecasting globally, as well as the significance of 4pi continuous monitoring of the Sun for more reliable space weather predictions overall.

Speaker: Evangelia Samara (NASA/GSFC)

12:30 Lunch

Transients, turbulence and variability in the heliosphere

63 From the Sun to the Heliosphere: The Complex Nature of ICMEs

First Name: Emilia
Last Name: Kilpua
Email Address: emilia.kilpua@helsinki.fi
Affiliation: University of Helsinki

All Authors: Emilia Kilpua

Abstract: Large-scale solar wind transients are fundamental drivers of heliospheric variability and space weather at Earth and other solar system planets. The most important of these are interplanetary coronal mass ejections (ICMEs), consisting of shocks, sheath regions, and driving ejecta, often featuring magnetic cloud signatures. This talk focuses on key properties of ICMEs and outlines differences between their various substructures. The emphasis will be on complexities and incoherence ICMEs manifest in the heliosphere, such as deviations from a coherent flux-rope structure and the presence of mesoscale features, in light of recent multi-spacecraft observations. The talk will also discuss the origins of deviations from the idealized flux-rope picture, arising partly from the Sun’s dynamo-driven magnetic field and partly from interplanetary evolution.

Speaker: Emilia Kilpua (University of Helsinki)

64 Interplanetary coronal mass ejections observed by Solar Orbiter (2020–2024) and their solar sources

First Name: Mateja
Last Name: Dumbovic
Email Address: mdumbovic@geof.hr
Affiliation: Hvar Observatory, Faculty of Geodesy, University of Zagreb

All Authors: Dumbovic, M., Martinic, K., Amaro, M.

Abstract: We identify, categorize, and analyze 77 interplanetary coronal mass ejections (ICMEs) observed in situ by Solar Orbiter between April 2020 and April 2024. For 28 of these events, we reliably associate their solar sources observed in remote white-light coronagraphs by applying a drag-based back-propagation model. In most of these associated cases, we further identify corresponding low-coronal signatures using observations from SDO/AIA, STEREO-A/EUVI, and/or Solar Orbiter/EUI. We perform a statistical analysis of the ICME properties and compare our results with previous studies conducted at 1 au and at smaller heliocentric distances. Our findings largely confirm previously reported ICME characteristics, while also providing new insights into the evolution of ICME sheaths. The compiled event list offers a valuable reference for future CME–ICME studies utilizing Solar Orbiter observations.

Speaker: Mateja Dumbovic (Hvar Observatory, Faculty of Geodesy, University of Zagreb)

65 Energetic Particle Transport in Structured and Multiscale Plasma Turbulence: Bridging Observations, Theory, and Simulation

First Name: Frederic
Last Name: Effenberger
Email Address: frederic.effenberger@rub.de
Affiliation: Ruhr-University Bochum

All Authors: ISSI Team #24-608

Abstract: Energetic particles in astrophysical plasmas, both in the heliosphere and in a variety of cosmic environments, interact with turbulence that is magnetised, intermittent, and inherently multiscale. Understanding how these turbulent structures govern particle transport and acceleration is key to interpreting cosmic ray propagation, space weather phenomena, and high-energy radiation signatures. Here, I report on intial results of our ISSI Team #24-608 that brings together experts in space plasma turbulence, particle transport modeling, and spacecraft data analysis to develop the next generation of physically realistic test-particle simulations. These models incorporate turbulence features constrained by heliospheric in-situ observations from Parker Solar Probe and Solar Orbiter, as well as numerical simulations resolving coherent structures like current sheets and flux ropes across broad dynamical ranges. We investigate the role of such intermittency and structure in modifying classical diffusion coefficients and enabling anomalous transport regimes. Our approach aims to move beyond idealised turbulence assumptions, providing testable predictions for particle fluxes and anisotropies in the heliosphere and beyond. These developments offer new perspectives on energetic particle dynamics across cosmic environments, with implications for galaxy-scale feedback processes and magnetised turbulence from star-forming regions to the intergalactic medium.

Speaker: Frederic Effenberger (Ruhr-University Bochum)

66 The Evolution of Turbulence in the Inner Heliosphere: Insights from the February 2022 Radial Alignment between Parker Solar Probe and Solar Orbiter

First Name: Julia
Last Name: Stawarz
Email Address: julia.stawarz@northumbria.ac.uk
Affiliation: Northumbria University

All Authors: Julia E. Stawarz, Lorenzo Matteini, Luca Sorriso-Valvo, Jaye Verniero, Raffaella D’Amicis, Lina Hadid, Utsav Panchal, Denise Perrone, Yeimy Rivera, Sergio Toledo Redondo, Robert Wicks

Abstract: Complex turbulent dynamics that facilitate energy transfer from large to progressively smaller scales play an important role in the solar wind. A key challenge in the study of solar wind turbulence is understanding how and to what extent the nature of the turbulent dynamics vary as the solar wind expands from the Sun. However, disentangling the dynamical evolution of the turbulence from variations in the properties of different solar wind streams and temporal variations in the source region of a given stream has traditionally been challenging in the solar wind. We examine an alignment between Parker Solar Probe and Solar Orbiter, which occurred in February 2022, to examine how solar wind turbulence evolves with radial distance. During this alignment the two spacecraft observed the same stream of solar wind plasma and likely the same plasma parcel at two radial distances. We focus on examining the intermittent character of the solar wind, providing insight into the evolving statistical distribution of structures, as well as the energy cascade rate to probe the evolving role of the turbulence in the energetics of the solar wind. The implications are examined in the context of recent measurements of the energy flux budget of the same solar wind stream by Rivera+ [(2024) Science, 385, 962-966].

Speaker: Julia Stawarz (Northumbria University)

67 online – Chasing Shocks with Solar Orbiter: Insights into Particle Acceleration During Solar Cycle 25

First Name: Domenico
Last Name: Trotta
Email Address: domenico.trotta@esa.int
Affiliation: European Space Agency (ESA), European Space Astronomy Centre (ESAC), Madrid, Spain

All Authors: Domenico Trotta

Abstract: Interplanetary (IP) shock waves propagate through the heliosphere as a result of solar activity. These shocks are key sites of energy conversion and particle acceleration and can be observed in situ through spacecraft measurements, providing a unique link to remote astrophysical environments and an excellent “natural laboratory” for testing still-debated acceleration mechanisms. The current fleet of heliospheric observers offers an unprecedented opportunity to study IP shocks, marking a “new golden era” for understanding their role in heliospheric energetics. In particular, Solar Orbiter provides high-resolution measurements in the suprathermal (above ~50 keV) range, opening a new observational window on how particles are accelerated out of the thermal population. In addition to presenting the statistical properties and trends of Solar Orbiter IP shocks up to the solar maximum of cycle 25, I will showcase specific events that uncovered new aspects of energetic particle production. I will show how leveraging state-of-the-art numerical simulations alongside multi-spacecraft observations makes it possible to probe the fundamental physics driving these acceleration processes in unprecedented detail. Together, these results offer fresh insights into how shocks energize particles across both heliospheric and astrophysical environments.

Speaker: Domenico Trotta (European European Space Agency (ESA), European Space Astronomy Centre (ESAC, Spain)

68 Alfvénic fluctuations in the solar wind: spherical polarisation, switchbacks and radial evolution

First Name: Lorenzo
Last Name: Matteini
Email Address: l.matteini@imperial.ac.uk
Affiliation: Physics Department, Imperial College London, UK

All Authors: Lorenzo Matteini

Abstract: Recent observations by both Solar Orbiter and Parker Solar Probe in the Inner Heliosphere have highlighted the key role played by Alfvénic fluctuations in the acceleration of the Solar Wind and in the energization of the plasma. In this presentation, I will briefly review the main properties of Alfvénic fluctuations observed in the near-Sun regions as well as their radial evolution. This includes the emergence of the state of “spherical polarisation” for the fluctuations, as well as the origin and evolution of magnetic switchbacks and their associated speed enhancements which are ubiquitous in wind coming from coronal holes and open field regions. I will then present and discuss results from recent simulations able to effectively reproduce these features in the expanding solar wind. Moreover, I will show how the main properties of spherically polarisation and switchbacks can be implemented in a simple model of Alfvénic fluctuations, reproducing their modulation with radial distance and thus explaining the main observational differences when comparing PSP and Solar Orbiter measurements.

Speaker: Lorenzo Matteini (Physics Department, Imperial College London, UK)

Coffee and Poster B

Transients, turbulence and variability in the heliosphere

69 online – Exploring Multiple Alfvénic Solar Wind Regimes at Solar Orbiter’s October 2022 Perihelion

First Name: Omkar
Last Name: Dhamane
Email Address: omkar.dhamane@inaf.it
Affiliation: INAF - Institute for Space Astrophysics and Planetology (IAPS) Cavaliere's Ditch Street, 100 00133 Rome (Italy)

All Authors: Omkar Dhamane, Raffaella D’Amicis, Simone Benella, Steph Yardley, Rossana De Marco, Roberto Bruno, Luca Sorriso-Valvo, Daniele Telloni, Denise Perrone, Christ Owen, Philip Louarn, Stefano Livi, Anil Raghav, Kishor Kumbhar, Utkarsh Sharma, Shubham Kadam, Urvi Naik

Abstract: Alfvénic fluctuations are a common feature of the solar wind, most prominently observed in fast wind streams, whereas slow wind typically displays lower Alfvénicity and greater variability. Nonetheless, the slow wind can occasionally exhibit strongly Alfvénic behavior, with fluctuations comparable to those found in fast wind. The occurrences of Alfvénic slow wind add complexity to the well-established differences between fast and slow solar wind, which span large-scale structures to small-scale turbulent dynamics. In this study, we investigate the distinct turbulent properties of fast wind and Alfvénic slow wind through a comparative analysis of their spectral characteristics. We utilize plasma and magnetic-field measurements from the Solar Wind Analyser (SWA) and Magnetometer (MAG) instruments onboard Solar Orbiter. By combining in situ measurements of solar wind plasma with remote-sensing observations of their sources, along with two-step ballistic backmapping, we show that Solar Orbiter is connected to a coronal hole followed by the boundary of the neighbouring active region. The solar wind variability detected in situ by Solar Orbiter during its October 2022 perihelion is driven by spatio-temporal changes in magnetic connectivity to multiple sources in the solar atmosphere. Our results show that certain Alfvénic slow-wind intervals preserve Alfvenicity, evident through high normalized cross helicity, fluctuations are close to equipartition of energy, weak magnetic compressibility, large magnetic and velocity fluctuation amplitudes comparable to those of fast Alfvénic streams, even though they exhibit lower bulk speeds and enhanced Coloumb collisional age. These findings pose important challenges for solar-wind models, which must explain how such intervals retain strong Alfvénic fluctuations despite originating from nearby source regions and displaying significant variations in other bulk plasma properties.

Speaker: Omkar Dhamane (INAF - Institute for Space Astrophysics and Planetology (IAPS), Italy)

70 Tracing the radial evolution of an Alfvénic slow wind and subsequent transient: observations from Solar Orbiter and Wind

First Name: Raffaella
Last Name: D'Amicis
Email Address: raffaella.damicis@inaf.it
Affiliation: INAF - IAPS

All Authors: R. D’Amicis, D. Trotta, O. Dhamane, A. Larosa, S. Benella, S. Yardley, R. De Marco, M. Laurenza, L. Sorriso-Valvo, D. Turner, D. Perrone, M. Velli, O. Panasenco, R. Bruno, D. Telloni, C. Owen, P. Louarn, S. Livi, J. Rodriguez-Pacheco, R. Wimmer-Schweingruber, T. Horbury

Abstract: Alfvénic fluctuations are ubiquitous in the solar wind and are thought to play a key role in several heliospheric processes, such as solar wind heating and acceleration, energetic particle acceleration, cosmic ray propagation, and geomagnetic activity. The ESA/NASA Solar Orbiter mission offers a unique opportunity to investigate the properties and origin of Alfvénic streams and their radial evolution. Owing to its orbital configuration, Solar Orbiter crosses the Sun–Earth line approximately once per year, enabling direct comparison with in-situ measurements detected at L1. We present a coordinated analysis of an Alfvénic slow wind stream observed by Solar Orbiter and Wind, subsequently overtaken by an ICME with a supercritical fast forward shock at its leading edge, propagating at ~ 1000 km/s at both spacecraft. Ballistic backmapping combined with high-resolution remote sensing observations allows us to identify its solar source region. Measurements from Solar Orbiter and Wind provide a robust framework to investigate the radial evolution of the stream’s turbulent properties, to assess the mechanisms responsible for the evolution of Alfvénicity and to address how the shock system evolves, focusing on the transmission of such Alfvénic fluctuations from up- to downstream at both heliocentric distances. We finally address the role of such a complex magnetic environment in the acceleration and variability of high energy (>1 MeV) protons, observed at both Solar Orbiter and Wind. These results offer new insights into the coupled evolution of turbulence, shocks, and energetic particles in the inner heliosphere.

Speaker: Raffaella D'Amicis (INAF - IAPS)

71 Solar Energetic Particles Observed by Solar Orbiter at High Latitude

First Name: George
Last Name: Ho
Email Address: george.ho@swri.org
Affiliation: Southwest Research Institute

All Authors: George C. Ho, Glenn M. Mason, Robert C. Allen, Samuel T. Hart, Athanasios Kouloumvakos, Robert F. Wimmer-Schweingruber, Javier Rodríguez-Pacheco, Raúl Gómez-Herrero

Abstract: Solar Orbiter began its high-latitude phase following a Venus gravity assist on February 18, 2025, reaching a maximum heliographic latitude of ~17° relative to the solar equator. A key objective of the mission is to investigate the physical processes governing Solar Energetic Particle (SEP) events, particularly the acceleration and transport of particles in the inner heliosphere. The Energetic Particle Detector (EPD) onboard Solar Orbiter has continuously monitored SEP activity over the past five years, including throughout this recent high-latitude phase. This study focuses on SEP events observed during 2025 while the spacecraft was at elevated latitudes. Beginning in March, EPD detected multiple SEP events, including several ³He-rich impulsive events and a few large, CME-associated events. Using a magnetic connectivity tool, we calculated the magnetic footpoints of Solar Orbiter on the solar surface to evaluate source-region connections. These observations help assess whether SEP propagation depends solely on the angular separation between source and observer in either longitude or latitude, or if it also reflects influences macroscale structures, such as proximity to the heliospheric current sheet or other large-scale solar structures.

Speaker: George Ho (Southwest Research Institute)

72 Compositional Variability in the November 2025 Solar Energetic Particle Events

First Name: Christina
Last Name: Cohen
Email Address: cohen@srl.caltech.edu
Affiliation: California Institute of Technology

All Authors: C.M.S. Cohen, G.M. Mason, R.A. Leske, G.C. Ho, R.F. Wimmer-Schweingruber, G.D. Muro, Z.G. Xu

Abstract: In the first half of November 2025, Parker Solar Probe, ACE, Solar Orbiter, and STEREO-A were distributed from 0.7 to 1 AU and ~127° in longitude as active region 14274 rotated across the solar disk emitting a large number of X-class flares, coronal mass ejections (CMEs) and several solar energetic particle (SEP) events, including the largest ground level enhancement (GLE) event of this solar cycle. GLE events often exhibit enhancements in several abundance ratios, including Fe/O and Ne/O, and the November 2025 GLE event appears to have that characteristic. Given the wide longitudinal distribution of the spacecraft, the magnetic connection to the CME-driven shocks, the detection of the shock passages and the associated CMEs is significantly different for each observer and may be reflected in the measured SEP composition. In this study, we examine the SEP composition as a function of energy and time for all four observers throughout this active period to investigate any dependence on longitude (and, to a lesser degree, radius).

Speaker: Christina Cohen (California Institute of Technology)

73 online – First results from the Aditya Solar Wind Particle Experiment (ASPEX) on-board Aditya-L1

First Name: Dibyendu
Last Name: Chakrabarty
Email Address: dipu@prl.res.in
Affiliation: Physical Research Laboratory

All Authors: Dibyendu Chakrabarty

Abstract: Aditya-L1 mission is the first observatory class mission from India to understand the Sun, solar wind, heliosphere and space weather. Launched on 02 September, 2023, the Aditya-L1 satellite was placed at a halo orbit around the first Lagrange point of the Sun-Earth system on 06 January, 2024. After performance verification of the payloads, science phase operation of the payloads was started. Aditya-L1 consists of seven experiments. Four experiments in Aditya-L1 are remote sensing experiments to study photospheric, chromospheric and coronal processes while three experiments are designed for in situ measurements of solar wind, energetic particles and interplanetary magnetic field (IMF). Aditya Solar wind Particle EXperiment (ASPEX) is one of the three in situ experiments to investigate solar wind and energetic particles. ASPEX consists of two spectrometers – Solar Wind Ion Spectrometer (SWIS) for low energy primary ion (protons or H+ and alpha particle or He2+) measurements and SupraThermal and Energetic Particle Spectrometer (STEPS) for measurements of suprathermal and solar energetic particles (SEP). Through these two spectrometers, ASPEX can measure solar wind ions from 100 eV to a few tens of MeVs. One of the novel features of ASPEX is its ability to have direction-resolved measurements from a 3-axis stabilized spacecraft giving rise an unprecedented opportunity to understand new aspects of solar wind properties, origin, acceleration, and anisotropy. In recent times, a number of insightful science results have been published based on the ASPEX measurements. Some of these results include the evidence of directional isotropy of quiet time suprathermal ions for short intervals, identification long duration energization of solar wind ions during the interacting interplanetary coronal mass ejection event (ICME) in May-2024 and connection of fluctuations in the direction anisotropy of energetic particle fluxes to the fluctuations in IMF. In this talk, some of these insightful results will be presented.

Speaker: Dibyendu Chakrabharty (Physical Research Laboratory)

Poster B

All these posters will be up on throughout both Wednesday and Thursday, during both coffee breaks and the dedicated evening poster sessions.