Speaker
Description
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.