Speaker
Description
First Name: Victor
Last Name: Réville
Affiliation: CNRS IRAP
All Authors: Victor Réville, Tristan Vergé, Naïs Fargette, Raffaella D’Amicis, Marco Velli, Philippe Louarn, Vincent Génot, Alexis Rouillard, Yi-Ming Wang, Éric Buchlin
Abstract: Alfvénic slow wind is a strange beast. First observed by Helios, it has only been confirmed within the last decade and has challenged our usual understanding and classification of solar wind streams. With a high absolute cross-helicity, indicating an imbalanced proportion of outward Alfvén waves, it resembles the coronal hole fast wind. It could thus find its origin in the core of very rapidly expanding small coronales holes that are known to give birth to slower and denser wind streams. Close to the Sun, Parker Solar Probe and Solar Orbiter have found many examples of such streams that seem less likely to survive up to 1 AU. In this work, we focus on a series of slow Alfvénic wind streams followed by a fast wind stream observed by Solar Orbiter between March and April 2022. We run a full MHD model of the global solar corona, with an Alfvén wave turbulence phenomenology, which provide self-consistently the solar wind speed, temperature and density, to assess the source properties of these wind streams. We find that a number of equatorial coronal holes with rapid expansion could be the origin of the plasma observed by Solar Orbiter. We also find that one Alfvénic slow streams could originate nearby an active region. We further study the distribution functions measured by PAS to assess the different kinetic properties of these streams.