SH036-0013
Solar Orbiter – Solar Wind Analyser (SWA) Suite: Initial Results of an Alpha-particle Relative Abundance Study within 0.5–1 AU
Monday, 14 December 2020
Poster
Lubomir Prech1, Tereza Durovcova1, Andrei Fedorov2, Jana Safrankova3, Zdenek Nemecek1, Philippe Louarn2, Christopher John Owen4, D O Kataria5, Roberto Bruno6, Stefano A Livi7, Jim M Raines8, Timothy Simon Horbury9, Helen O'Brien9, Alain Barthe2 and The International SWA and MAG Teams on Solar Orbiter, (1)Charles University, Prague, Czech Republic, (2)IRAP, CNRS, Toulouse, France, (3)Charles University, Prague, 180, Czech Republic, (4)University College London, Mullard Space Science Laboratory, Dorking, United Kingdom, (5)University College London, Mullard Space Science Laboratory, London, United Kingdom, (6)INAF-IFSI, Rome, Italy, (7)SwRI, San Antonio, TX, United States, (8)University of Michigan, Ann Arbor, MI, United States, (9)Imperial College London, Department of Physics, London, SW7, United Kingdom
Abstract:
Alpha particles play an important role in solar wind dynamics. Their relative abundance (A
He) and relative drift to protons are usually associated with the solar wind source region. However, observations near the Earth indicate that these relative properties could also be altered by processes occurring in the interplanetary space, such as interactions of solar wind streams with different speeds. When the fast solar wind pushes up against the slow solar wind ahead of it, the co-rotating interaction region (CIR) is formed. Mirroring of the multicomponent solar wind in the converging magnetic field that develops within CIRs could lead to changes of A
He and reduction of the alpha-proton relative drift. When the high-speed stream outruns the slow solar wind, the co-rotating region of rarefied solar wind (CRR) is formed where A
He variations were also observed. Since CRRs are associated with the regions of small longitudinal extent on the Sun, these variations probably arise along the path from the Sun to Earth.
Passing the first perihelion, Solar Orbiter – the ESA/NASA common mission to study the Sun and inner heliosphere – entered the cruise phase in June 2020. Currently, two sensors of the Solar Wind Analyser Suite – Proton-Alpha Sensor (PAS) and Heavy Ion Sensor (HIS) provide valuable data on alpha-particle properties along the outbound part of the first Solar Orbiter orbit. In this contribution, we briefly describe the PAS processing methods related to alpha particles and existing caveats and we present the initial results on the alpha particle relative abundance observations. Also, we would like to combine the Solar Orbiter data on a half a way to the Sun with observations at 1 AU (Wind, ACE) to study the mechanisms leading to variations of alpha-proton properties.
