During magnetic reconnection in collisionless plasma strong electron jets often emanate from the electron diffusion region (EDR). Given the results of the influential Sweet‐Parker reconnection model (derived for a collisional plasma), it is commonly assumed that these electron jets are driven by the reconnection electric field. In contrast, kinetic models and simulations have suggested that...
Collisionless shocks are among the most fundamental nonlinear processes in plasmas. Generated by violent interactions of supersonic plasma flows with the interstellar medium or planetary magnetospheres, collisionless shocks are inferred to heat the plasma, amplify magnetic fields, and accelerate electrons and protons to highly relativistic speeds. However, the exact mechanisms that control...
Recent advancements in the state-of-the-art modelling of relativistic astrophysical plasma via numerical simulations are presented. In particular, I will focus on a novel implementation of a genuinely 4th-order accurate finite volume scheme for the solution of the relativistic MHD equations in the presence of a finite conductivity. The method has been successfully implemented and validated in...
Space plasma simulations are typically categorized into fluid and kinetic models, which are employed for modeling macroscopic and microscopic phenomena, respectively. Fluid models consider only lower-order moments (usually up to the second order), whereas kinetic models have degrees of freedom that are more than one order of magnitude larger. This introduces a significant gap between the two...
ULF waves are MHD waves observed in the Earth's inner magnetosphere, especially oscillations with periods ranging from a few seconds to a few hundred seconds. The excitation and propagation processes of ULF waves have been extensively studied. Field line resonance (FLR) is a process in which Alfvén waves resonate with fast modes that are excited at the magnetopause and propagate toward the...
In computational plasma physics kinetic models are used to simulate plasma phenomena where small scale physics is expected to be of importance. These models contain the full information of the particle velocity distribution function but are computationally expensive. Therefore, computationally cheaper models are utilized, which can then be deployed to larger scales, e. g. 10-moment fluid...
The intricate energy exchanges within the Sun-Earth system, including geomagnetic storms, profoundly influence both ground and space technologies crucial for modern society. Effective forecasting and mitigation of space weather necessitate vigilant monitoring of the Earth's magnetosphere. However, this task is hindered by limited in-situ satellite measurements and ground-based observations....
Mirror waves are widely observed in space plasma environments. The mirror instability may occur in anisotropic plasmas where the perpendicular temperature exceeds the parallel temperature. An important characteristic of mirror waves is the anticorrelation between plasma density and magnetic field perturbations. Moreover, recent observations have indicated an anticorrelation between temperature...
Alfvén waves play an important role in coronal heating and solar wind acceleration. Despite the recent progress of theoretical and observational studies on Alfvén waves, their dissipation processes have not been fully understood. Parametric Decay Instability (PDI) is a coupling process between waves in which a large-amplitude, forward-propagating Alfvén wave resonates and decays into a...
Galactic cosmic rays (GCRs) are charged particles with extremely high energies originating from outside the heliosphere. Their passage through the solar wind is affected by many long and short term factors, including transient structures such as coronal mass ejections (CMEs). The short term decrease in GCR flux caused by CMEs, and observed by charged particle detectors on spacecraft and...
Jets in active galactic nuclei (AGN) are known for their intense X-ray and gamma-ray emission, originating from non-thermal particles. These sources are also linked to high-energy neutrino events and are considered potential sites of ultra-high-energy cosmic ray production. Accelerated particles can be generated in shock waves formed in collisionless AGN plasmas. We study oblique mildly...
This talk will be a review of the principle space and astrophysical plasma relevant experiments undertaken at Wisconsin Plasma Physics Laboratory (WiPPL) since the last IPELS meeting. WiPPL is a collaborative user facility, operating the Big Red Ball (BRB) and the Madison Symmetric Torus (MST) out of the Physics Department at the University of Wisconsin, hosting users from around the world. I...
This study provides a new numerical method for relaxation of the Courant condition and correction of numerical errors in the Finite-Difference Time-Domain (FDTD) method with the time-development equations using higher-degree difference terms. The FDTD method (Yee 1966) is a numerical method for solving the time development of electromagnetic fields by approximating Maxwell's equations in both...
The objective of this project is to investigate shocks through Particle-In-Cell (PIC) simulations, particularly focusing on intermediate Mach. By delving into the transition between low and high Mach number instabilities, we aim to gain valuable insights into shock dynamics and electron behavior. Through experimentation and analysis, we hope to improve our understanding of shocks and electron...
In large-scale simulations, that also include spectral cosmic-ray physics, high-energy protons and electrons accelerated at the shocks of supernova remnants have to be described by a sub-grid model. Usually, the injected cosmic rays are represented by a simple power-law spectrum in momentum space. However, in the recent past several models for more realistic cosmic-ray spectra from supernova...
Plasma in space are omnipresent, but generally found in a partially ionized state only. Thus, we need to consider the interaction between ionized and neutral gases. Since the coupling between both gases is mediated via collisions we expect, on scales shorter than their collision frequency, the gases to increasingly decouple while on larger scales the gases to move in unison. This has immediate...
Ambipolar electric fields are often observed in compressed plasma layers throughout the near-Earth space environment and have been shown to be important for plasma flows, wave generation, broadband turbulence, and dissipation mechanisms. When an ambipolar electric field self-consistently forms perpendicular to a background magnetic field, E×B velocity shear is generated. Shear-driven...
The standard magnetorotational instability (SMRI) has been regarded as the most promising instability responsible for the turbulence required to explain the fast accretion observed across the Universe. However, unlike other fundamental plasma processes such as Alfvén waves and magnetic reconnection, which have been subsequently detected and studied in space and the laboratory, SMRI remains...
During transient instabilities in a 2 eV, highly collisional MHD-driven plasma jet experiment, evidence of a 6 keV electron tail was observed via x-ray measurements. The cause for this unexpected high energy tail is explored using numerical simulations of the Rutherford scattering of a large number of electrons and ions in the presence of a uniform electric field that is abruptly turned on as...
Magnetic reconnection is a ubiquitous fundamental process in space and astrophysical plasmas that rapidly converts magnetic energy into some combination of flow energy, thermal energy, and non-thermal energetic particles. Over the past decade, a new experimental platform has been developed to study magnetic reconnection using strong coil currents powered by high power lasers at low plasma...
Mini-magnetospheres are ion-scale structures that are ideal for studying the kinetic-scale physics of collisionless space plasmas. Such ion-scale magnetospheres can be found on local regions of the Moon, associated with the interaction of the solar wind with the lunar crustal magnetic field. In this work, we report on the experimental study of magnetic reconnection in laser-driven lunar-like...
In two toroidal plasma merging experiments with high guide field ($B_{t}$ >> $B_{p}$), the ion heating energy by magnetic reconnection is shown to scale with the reconnecting magnetic energy ($B_{rec}^{2}$/2$\mu_{0}$) where $B_{rec}$~$B_{p}$. This $B_{rec}^{2}$- scaling of ion heating energy by reconnection can be understood by the fact that in the reconnection downstream the ion energy is...
In a prototypical two-dimensional antiparallel reconnection geometry, we experimentally verify a well- known Petshek-type reconnection layer of double wedge structure and explained by two-fluid dynamics. In a two-fluid reconnection layer, as electrons and ions move into the reconnection layer with different paths, the magnetized electrons penetrate deep into the reconnection layer generating a...
Shock waves are ubiquitous in astrophysical, space and laboratory plasmas and often include an embedded, dynamically significant magnetic field. This magnetic field modifies the RH shock jump conditions, and allows dissipation mechanisms specific to magneto-hydrodynamics, such as Ohmic heating, to contribute to shock shaping. In fact, low Mach number shocks can be shaped exclusively by...
The transport of energy and momentum and the heating of plasma particles by waves and turbulence are key ingredients in many problems at the frontiers of heliospheric and astrophysics research. This includes the heating and acceleration of the solar wind, the observational appearance of black-hole accretion flows on event-horizon scales, and the properties of the hot, diffuse plasmas that fill...
We investigate nonlinear processes in the generation of whistler-mode chorus emissions in the Earth's inner magnetosphere by a series of electron hybrid code simulations. We also study propagation properties of chorus emissions under the presence of duct structure in the magnetosphere. Chorus emissions are coherent whistler-mode waves with varying frequencies in the typical frequency range of...
Paper: Issan O, Koshkarov O, Halpern F, Kramer B, Delzanno GL (2024). Anti-symmetric and Positivity Preserving Formulation of a Spectral Method for Vlasov-Poisson Equations. Journal of Computational Physics (in press). doi: 10.1016/j.jcp.2024.113263
Plasma wave theory involves understanding how the perturbation of particle orbits by mean-field waves produces charge densities and currents that self-consistently create the mean-fields. Exact solutions are known in only a few special cases. However, given this self-consistent relationship, it is natural to ask – how much about the wave fields in a given region of space can be known by...
Magnetic reconnection is an ubiquitous phenomenon observed in laboratory, fusion and space plasmas. It is usually accompanied by the energy conversion between electromagnetic fields and plasmas [1]. Recently, a new regime called “electron-only magnetic reconnection” (e-rec hereafter) was observed and studied in the Earth’s magnetosheath [2] and in laboratory plasmas [3]. The novelty of e-rec...
We present the formation of positronium (Ps) through charge-exchange of magnetically confined positrons and background gas in the laboratory. A bunch of 10⁵ positrons is extracted from a buffer-gas trap and injected into the dipole field of a permanent magnet trap with E×B drifts [1]. Once injected, the positrons are confined through a combination of magnetic mirroring and electrostatic...
Coherent radio waves from pulsars bring information about relativistic extremely-magnetized pair plasmas in neutron star magnetospheres because the waves originate at plasma kinetic scales. Though various radio emission mechanisms have been proposed in the last decades for their interpretation, many lack the inclusion of self-consistent wave--wave and particle--wave interactions, emission...
Alfvénic fluctuations - fluctuations with magnetic-field and velocity fluctuations perpendicular to the background magnetic field which are proportional to each other - are thought to be ubiquitous in magnetized astrophysical plasma environments and are observed across scales in our own solar wind. Recent theoretical work by Mallet et al [1] proposes a mechanism by which small-scale, oblique...
In controlled laboratory setups, when lasers interact with solid or gaseous targets, various phenomena such as shock formation, plasma instability, and magnetic reconnection can be observed. Understanding the behavior of electromagnetic fields in plasmas is crucial in these experiments. To measure these fields, scientists utilize a method called ion radiography, also known as proton imaging....
The Magnetized Plasma Research Laboratory (MPRL) at Auburn University explores fundamental plasma and complex/dusty plasma phenomena covering a large parameter regime from unmagnetized plasmas to strongly magnetized plasmas with a mission to serve as an open access, multi-user collaborative research facility. The centerpiece of the laboratory is the Magnetized Dusty Plasma Experiment (MDPX), a...
Advanced thrusters are needed for deep space missions to Mars and beyond. For such thrusters, it is critical to determine how to generate large thrust-to-power at sufficiently high specific impulse with long lifetime and flexibility in propellant. To address these challenges, we are exploring a new electrodeless Magnetic Reconnection Thruster (e-MRT), which will use asymmetric,...
Nonthermal particle acceleration is believed to account for a large portion of the energy dissipated during magnetic reconnection. However, this process remains poorly understood, and laboratory observation of non-thermal acceleration remains limited. Here, we present a novel design for a multi-channel electron energy analyzer for studies of electron acceleration in magnetic reconnection. This...
Local precipitation loss due to pitch angle scattering by magnetospheric waves is the focus of our analysis. Plasma waves can alter the course of a charged particle and influence a previously trapped electron from the magnetosphere to penetrate the Earth’s upper atmosphere. Once in the upper atmosphere, a charge particle can ionize air molecules leading to the destruction of ozone and...
It is known that magnetic reconnection can occur in current sheets generated by collisionless turbulence in space and astrophysical plasmas, a process known as turbulence-driven reconnection. The importance of this process for the turbulence properties is, however, still not well understood. Although significant simulation work has been done on this topic in 2D and at MHD and ion-scales, the...
The emerging computable devices, graphical processing units (GPU), are gradually applied in the simulations of space physics for their high efficiency. Here we present a fully kinetic particle-in-cell (PIC) simulation code running on GPU devices called GPIC, which adopts CUDA Fortran programming. Compared with the simulations running on the Intel Xeon Gold processor, our program working on...
Particle-in-cell (PIC) simulation is an important tool to study collective behavior of charged particles in space. At start of the simulation, it is necessary to initialize particle velocities, by using random variables. The distribution of particle velocities may vary from problem to problem. We may want to use a Maxwell distribution in many cases, a kappa distribution for heliospheric...
Numerical methods for solving the relativistic motion of charged particles with a higher accuracy is an issue for scientific computing in various fields including plasma physics. The classic fourth-order Runge-Kutta method (RK4) has been used over many years for tracking charged particle motions, although RK4 does not satisfy any conservation law. However, the Boris method [Boris 1970] has...
I will describe Astrophysical Hybrid-Kinetic simulations with the flASH code (AHKASH) - a new Hybrid particle-in-cell (PIC) module developed within the framework of the multi-physics code FLASH. Our new second-order accurate hybrid PIC method uses the Boris particle integrator and a predictor-predictor-corrector algorithm for advancing the Hybrid-kinetic equations. It also employs the...
Particle-in-Cell simulations can provide a possible answer to an important key issue of astrophysical plasma jets, i.e., how a toroidal magnetic field affects the evolution of pair and electron-ion jets associated to the acceleration of particles. We show that Weibel, mushroom, and kinetic Kelvin-Helmholtz instabilities excited at the linear stage, generate a quasi-steady electric field...
The heat flux of electrons plays a crucial role in energy transport processes in collisionless or weakly collisional plasma of the solar wind. Early observations indicated that the collisional Spitzer-Härm law cannot describe the heat flux in the solar wind. Various mechanisms for regulating heat flux in the solar wind have been proposed, such as the interaction of electrons with whistler...
The correlation between linear and nonlinear ion acoustic waves (IAWs); i.e. solitary waves, observed in the vicinity to the Sun is still an open question. These electrostatic structures have a high electric field and are regularly spaced (Mozer et al. 2021; Graham et al. 2021). We study the onset of the ion acoustic instability in a parameter regime compatible with these observations. In the...
NASA’s Magnetospheric Multiscale mission (MMS) has provided and continues to provide heretofore unimaginable insight into the kinetic machinery of the magnetic reconnection process. These successes are based on innovative combinations of extreme-precision observations of magnetic reconnection at the Earth’s magnetopause and inside the nightside magnetotail, with concurrent theoretical analyses...
With the advent of Ultra-High Energy gamma-ray astronomy (photons above 100 TeV energies) it is at last possible to directly probe the most extreme particle accelerators in our galaxy. Two source classes have emerged as highly prominent producers of the cosmic rays above PeV energies, namely massive stellar clusters and microquasars, adding a new dimension to the long held supernova remnant...
Magnetic reconnection serves as a crucial mechanism for generating various sources of free energy for waves and instabilities, including pressure gradients, temperature anisotropies, and large electric currents. In this talk, we focus on recent observations of waves in laboratory reconnection experiments, particularly in the Magnetic Reconnection Experiment (MRX).
Whistler waves, originating...
Here we report the particle acceleration and heating of magnetic reconnection under the influence of high guide field in the merging spherical tokamak formation experiments in ST40 and TS-6. In addition to the extension of ion heating scaling $\Delta T_i\propto B_{rec}^2$ in keV range, our recent experiments explored the following 3 new findings using 96CH/320CH ion Doppler tomography and...
Numerical schemes that preserve the structure of the underlying kinetic
equations can provide new insights into the long time behavior of plasmas. Implicit schemes offer the possibility to simulate large scale systems where the characteristic plasma parameters, skin depth and plasma frequency, are underresolved. A very efficient semi-implicit energy-conserving scheme can be derived for the...
Variation of plasma density and magnetic field in space plasma drives the development of temperature anisotropies in the component species. A sufficiently large anisotropy of electrons in the direction perpendicular to the ambient magnetic field causes whistler and mirror instabilities to grow. It has been suggested that the anisotropy of the electron species can affect the growth of...
The exact plasma composition of astrophysical jets remains an open question to date. Jets originate near compact objects, protostars, and active galactic nuclei. Hence, the composition of the jets depends upon the environment in which they form, and it is expected that the composition should affect the dynamics and morphology of the jets. In this work, we aim to investigate the effect of...
Solar activities have an extraordinary impact on interplanetary space, enriching the plasma dynamics including turbulent heating of various species. The small fraction of alpha particles is believed to play a significant role in the turbulent dynamics of the solar wind. Here we present fully kinetic particle-in-cell (PIC) simulations to reveal the influences of the alpha particles in decaying...
Planetary radiation belts form a major hazard to orbiting satellites and predicting their variability is a primary goal of space weather forecasting efforts. While radiation belt dynamics are well-approximated by the Fokker Planck diffusion equation representing transport in energy, radial distance and pitch angle, more realistic magnetic field models and diffusive-advective transport have...
A 3D implicit particle-in-cell (PIC) simulation has been used to model the Earth’s magnetosphere to investigate the development of the ring current when electron kinetics are included. Initialized with starting conditions from a global magnetohydrodynamic (MHD) simulation, the computational burden for modeling the entire magnetosphere using a PIC code is reduced and allows the system to...
Historically, dark matter searches have primarily focused on hunting for effects from two-to-two scattering. However, given that the visible universe is primarily composed of plasmas governed by collective effects, there is great potential to explore similar effects in the dark sector. Recent semi-analytic work has shown that new areas of parameter space for dark U(1) and millicharged models...
Ultra-low frequency (ULF) waves contribute significantly to the dynamic evolution of Earth's magnetosphere by accelerating and transporting charged particles within a wide energy range. A substantial excitation mechanism of these waves is their drift-bounce resonant interactions with magnetospheric particles. Here, we extend the conventional drift-bounce resonance theory to formulate the...
Energy dissipation in collisionless plasmas is one of the most outstanding open questions in plasma physics. Magnetic reconnection and turbulence are two phenomena that can produce the conditions for energy dissipation. These two phenomena are closely related to each other in a wide range of plasmas. Turbulent fluctuations can emerge in critical regions of reconnection events, and magnetic...
Magnetic Reconnection is the ubiquitous astrophysical process in which a plasma rapidly converts magnetic field energy into a combination of flow energy, thermal energy and non-thermal energetic particles. Various particle acceleration mechanism (including Fermi acceleration, betatron acceleration, parallel electric field acceleration, out-of-reconnection plane acceleration) have been...
TOI-700 d is the first Earth-sized planet in the habitable zone (HZ) discovered by the Transiting Exoplanet Survey Satellite. Here, we assess whether a Venus-like exoplanet at the TOI-700 d location could retain an atmosphere for a time comparable to the age of the host star based on multispecies magnetohydrodynamics simulations [1]. We investigate the effects of X-ray and EUV (XUV) radiation...
The Universe was born without magnetic fields, yet in the modern Universe dynamically important magnetic fields are ubiquitous. The standard model of magnetogenesis explains this with small-scale dynamo (SSD) amplification of weak primordial fields to the levels we see today, followed by larger-scale coherence generated through large-scale dynamos (LSDs). This model, however, faces challenges...
Electron-scale physics is often the key ingredient that helps to disentangle complex plasma measurements. In this talk, I highlight the synergies between in-situ observations, simulation models and laboratory experiments, characterizing the role that localized plasma processes can have in regulating the large-scale dynamics and evolution of a macroscopic system. I focus on modeling the kinetic...
We found by three-dimensional global radiation magnetohydrodynamic simulations that during the hard-to-soft state transition observed in stellar mass black hole candidates and in active galactic nuclei, toroidal magnetic field is amplified around the interface between the hard X-ray emitting hot accretion flow near the black hole and the radiatively cooled outer disk. Since the magnetic...
The presence of charged dust particles in the space environment is well-known. From observations of structures in the dust tails of comets and the Voyager observations of radial structures (“spokes”) in Saturn’s rings, the role of charged dust in the solar system has been the subject of intense study for decades. More recently, the presence of flowing magnetized dust clouds has been...
Steep pressure gradients in a magnetized plasma can induce a variety of spontaneous low frequency excitations such as drift-Alfven waves and vortices. We present results from basic experiments on energy and particle transport in magnetized plasmas with multiple heat sources in close proximity [1]. The experiments were carried out at the upgraded Large Plasma Device (LAPD) operated by the Basic...
In earlier papers (Sauer and Sydora, 2015, 2016) it has been shown that an electron current in a plasma is directly linked to the formation of Langmuir oscillations at the electron plasma frequency ω_e. The current may arise due to a relative drift between electrons and protons or by a drifting electron population. No kind of beam instability should be involved. The excitation of ...
The Juno satellite is the first satellite in polar orbit around Jupiter, leading to unprecedented coverage of Jupiter’s magnetosphere. During the Juno extended mission, the satellite samples the polar regions of Jupiter at altitudes of less than 0.5 Jovian radii. Observations from Juno have indicated very low densities, as low as 10−3 cm−3, on polar cap field lines at Jupiter (Sulaiman et...
Collisionless low Mach number shocks are abundant in astrophysical and space plasma environments, exhibiting complex wave activity and wave-particle interactions. In this paper, we present 2D Particle-in-Cell simulations of quasi-perpendicular nonrelativistic (Vsh=(5500-22000) km/s) low Mach number shocks, with a specific focus on studying electrostatic waves in the shock ramp and the...
The magnetic Rayleigh Taylor instability (MRTI) is ubiquitous in a wide range of astrophysical and laboratory systems. However, the evolution and the dynamics of MRTI is not fully understood. Magnetic fields play a crucial role in the instability dynamics of these systems. Towards understanding the interplay between gravity and magnetic forces on the evolution of instability, we study MRTI...
Although turbulent dynamo processes can amplify magnetic fields to the strength observed in astrophysical situations, how seed magnetic fields are generated in the first place is still a mystery. We show that by analyzing the evolution of canonical vorticity that the canonical battery effect is responsible for seed magnetogenesis. The process generalizes popular magnetogenesis mechanisms,...
Interaction between the solar wind and upper atmosphere facilitates various atmospheric escape processes from terrestrial planets. The escape rate depends on various conditions such as the distance from the Sun, solar activities, planetary size, atmospheric composition, and intrinsic magnetic field. The atmosphere retention is one of necessary conditions for habitable terrestrial exoplanets....
Axial merging of two torus plasmas is utilized to form a high ion temperature plasma in fusion devices through energy conversion by magnetic reconnection. In a spherical tokamak merging experiment [1] in which the guide magnetic field is more than ten times larger than the reconnecting magnetic field, the inductive reconnection electric field is almost parallel to the magnetic field...
As Quantum Computing systems continue their maturation, their addition to the spectrum of HPC accelerators slowly becomes more viable. For them to be usable, though, we require substantial efforts to integrate the quantum and the HPC ecosystem. On the hardware side, the needed efforts seem straightforward - integrating the quantum control system with lowest possible latency into the HPC...
During magnetospheric substorms, plasma from magnetic reconnection in the magnetotail is thought to reach the inner magnetosphere and form a partial ring current. We simulate this process using a fully kinetic particle-in-cell (PIC) numerical code starting from a global magnetohydrodynamics (MHD) model run for nominal solar wind parameters and a southward interplanetary magnetic field. The PIC...
Turbulence and magnetic reconnection are intrinsic to space and astrophysical plasmas. Recent observations revealed a novel type of reconnection occurring in the turbulent Earth’s magnetosheath, dubbed “electron-only reconnection” [Phan 2018]. This distinctive form of reconnection occurs in the absence of ion outflows, signifying a reconnection event without an Ion Diffusion Region (IDR). 2D...
Weakly magnetized plasmas are found in natural plasmas such as the solar wind, but also in laboratory applications, e.g. in the edge of fusion plasmas. Ordering assumptions made in gyrokinetic theory—like low frequency or moderate gradients—may be challenged, particularly for the heavier ions. To overcome these limitations, the group derived equations for a hybrid model that includes fully...
Coronal Mass Ejections (CMEs) are major drivers of Space Weather (SWx) effects on Earth, and predicting their arrival is a major aspect of SWx forecast. Several CME propagation models have been developed for this purpose, but the overall arrival time error still exceeds 12 hours. In this study, we aim to improve these predictions by employing machine learning (ML) techniques that utilize the...
Turbulence is ubiquitous throughout different space plasma environments, facilitating the cascade of energy down to smaller and smaller length scales. That said, the different parameter regimes at which these plasmas exist have a significant effect on the way the cascade develops- turbulence at the MHD limit will not have the same attributes as turbulence at the kinetic limit. For instance,...
Terrella (“little Earth” [1]) is a metalized spherical magnet with a dipolar magnetic field that can serve as a laboratory model of compact space objects with large magnetic fields (neutron stars, white dwarfs, etc.). In our case, Terrella is a spherical neodymium magnet with a diameter of $19~\mathrm{mm}$ supplied by high voltage (up to $400\,\mathrm{V}$) at a pressure between...
Collisionless shocks are ubiquitous objects in the universe. Many of these shocks are magnetized due to preexisting magnetic fields in the upstream, which is the case for the Earth’s bowshock in heliophysics and supernova remnants. Despite decades of observations and numerical simulations, there remains no clear understanding on how energy is partitioned between electrons and ions across a...
Our multi-view soft X-ray measurement system detected for the first time high-energy electrons localized at the X-point of two merging tokamak plasmas. We found their energies increase with the guide toroidal field. These electrons are considered to be accelerated by the reconnection electric field along the guide magnetic field.
Under a high guide field, the reconnection electric field is...
Neutron stars are rotating objects with a strong magnetic field. The consequent induced field in the rotating reference frame is expected to support the creation of pair plasma in the vicinity of the neutron star. Presumably, electrons and positrons reside in separated domains above the poles and around the equator. This model is supported by several fully kinetic particle-in-cell (PIC)...
Using tracer particles propagating in an environment that simulates the accretion disk surrounding a black hole, this work aims to provide insight into the confinement of high energy particles in the galaxy NGC 1068 ( J. Bland-Hawthorn et al., 1997, Astrophysics and Space Science; K. Murase, 2022, The Astrophysical Journal Letters ), which is believed to be the source of the neutrino...
The interactions between the solar wind and planetary magnetospheres dictate the planetary space environments. Three-dimensional global hybrid simulations allow us to better understand such interactions by considering particle kinetic effects in global configurations. I will talk about some of our simulation results for Earth's and Mercury's magnetospheres, including 1) Flux ropes and their...
Global simulations have become an invaluable tool for studies of planetary magnetospheres, aiding in interpreting satellite observations, uncovering new physics and processes, and deepening our understanding of the fundamental magnetospheric behavior. Because of their relatively large system sizes, planetary magnetospheres are normally simulated with ideal magnetohydrodynamics (MHD) models,...
Analytical and numerical models of the linear and nonlinear stages of evolution of different types of short scale low frequency waves in the mid-latitude ionosphere will be presented. Density gradients and velocity shears observed in the Earth’s ionosphere are likely to undergo Raleigh-Taylor (RT) or Kelvin-Helmholtz (KH) type instabilities, but typically live longer than expected. Possibility...
We present a physical mechanism for generating GeV protons in the Inner Jovian Magnetosphere [1], which may contribute to formation of the proton radiation belts. The mechanism consists of two nonlinear processes called anomalous trapping and relativistic turning acceleration (RTA) and involves a special form of nonlinear wave trapping by electromagnetic ion cyclotron (EMIC) waves. Necessary...
The dynamics of Bursty Bulk Flows (BBFs) is an outstanding magnetosphere-ionosphere-thermosphere (MIT) coupling problem associated with sudden magnetic field topology reconfiguration and explosive current formation, particle acceleration, and energy release in the magnetosphere, and is believed to be playing a central role in geomagnetic disturbances, such as substorms. Using a two-way coupled...
Langmuir probes are essential diagnostic instruments used in laboratory plasma experiments and space missions. While traditional Langmuir probes are limited by their sampling rate due to voltage sweeping processes, the multi-needle Langmuir probe (m-NLP) instrument has been developed to overcome this limitation, offering a higher sampling rate that is particularly advantageous for in-situ...
Narrowband (∆f < 0.1 fcp), high-frequency (0.9 fcp < f < fcp) electromagnetic ion cyclotron (EMIC) waves, or HFEMIC waves for short, are a new type of EMIC waves found in the Earth’s inner magnetosphere. Observations suggest that they can be excited by low energy (< ~100 eV), very anisotropic protons. Here, we explore the instability threshold condition and hybrid simulations of HFEMIC waves,...
Mars lacks a global magnetic field but it has a weak induced magnetosphere resulting from the solar wind interaction with its upper atmosphere. Despite its slender spatial profile, it can facilitate various plasma wave activities. The Langmuir Probe and Waves (LPW) experiment aboard the MAVEN (Mars And Volatile EvoluioN) spacecraft has observed electrostatic solitary structures in the Martian...
Jupiter possesses the most hazardous radiation belt in the solar system which is responsible of trapping ultra-relativistic protons (~ 100 GeV), electrons (~ 100 MeV) and heavy ions like $O^+$, $O^{++}$, $S^+$, $S^{++}$, $S^{+++}$ (~100 MeV). Depending on the energy of the charged particles and the strength of Jupiter's magnetic field, these particles are either lost or trapped as they enter...
Kinetic Alfvén waves (KAWs) have long wavelengths parallel to magnetic field lines and perpendicular wavelengths comparable to the ion Larmor radius. KAWs possess a parallel electric field component ($\delta E_{\parallel}$) that accelerates electrons along magnetic field lines [e.g., Hasegawa, 1976]. These waves are frequently observed in the terrestrial magnetosphere during substorms [e.g.,...
High fidelity numerical simulations are necessary to drive design choices for future fusion devices, e.g. the ITER tokamak. XGC is a gyrokinetic Particle-in-Cell (PIC) application optimized for modeling the edge region plasma. The Coulomb collision operator is one of the more computationally expensive components of XGC. It requires linear solutions for a large number of small matrices with an...
The 'picket fence' is a captivating visual phenomenon characterized by vibrant green streaks in the subauroral sky, often appearing below a rare purpleish-white arc called STEVE (Strong Thermal Emission Velocity Enhancement). Recent studies suggest that, despite its aurora-like appearance, the picket fence may be driven NOT by magnetospheric particle precipitation but instead by local...
Two-dimensional full particle-in-cell simulations of pickup ion mediated oblique shocks were conducted with unprecedentedly long simulation times (over 100 times the inverse ion gyro frequency) and large system sizes (2000 times the ion inertial length) along the shock normal direction. An oblique shock refers to a shock where the angle between the shock normal direction and the upstream...
Magnetic reconnection has long been known to be the most important mechanism not only for the mixing of plasmas by changing the magnetic field topology, but also for the release of magnetic field energy into plasma kinetic energy. In addition, part of the heated plasma can be accelerated to energies much higher than the thermal energy during reconnection. So far, the energy partitioning of...
The grand challenge being pursued by the APEX (A Positron Electron eXperiment) Collaboration is to create and study cold, confined, strongly magnetized, matter-antimatter “pair plasmas” in the laboratory. This unusually simple, symmetric type of plasma has been the subject of theory/simulation predictions, in part motivated by astrophysical e+e- pair plasmas, going back over four decades; we...
Magnetic fields can play an important role in the energy balance and formation of gas structures in galaxies. However, their dynamical effect on the rotation curve of galaxies is immensely unexplored. We investigate the dynamical impact of the known magnetic arms of NGC 6946 on its circular gas rotation traced in HI, considering two dark-matter mass-density models, ISO, and the universal NFW...
The phenomenon of energy dissipation in collisionless plasmas such as the solar wind remains a subject of incomplete understanding within the scientific community. Central to this enigma is the intermittent nature of magnetic structures, which seems to play a pivotal role in the energy cascade process. Achieving a comprehensive comprehension of energy transfer and dissipation in the solar wind...
We estimate the global impact of storms on the global structure and dynamics of the night side plasma sheet from observations by the NASA mission THEMIS. We focus on an intense storm occurring in December 2015 triggered by interplanetary coronal mass ejections (ICMEs). It starts with a storm sudden commencement (SSC) phase (SYM-H$\sim$+50nT) followed by a growth phase (SYM-H$\sim$-188 nT at...
Collisions between charged and neutral particles in plasma can lead to energy and momentum transfer, which can affect plasma temperature and density profiles. Understanding and controlling these transport properties is necessary to achieve and maintain the conditions required for nuclear fusion reactions to occur in a tokamak.
In this study, we investigate collision frequency and energy...
The interaction region between the solar wind and planetary atmospheres is a critical window for investigating planetary evolution. Mars, with its complex magnetic environment, offers an ideal setting for studying this interaction region. Within this region, particles of varying energies interact in a complex plasma environment, facilitating diverse material and energy transfer processes. This...
