Magnetic reconnection as a mechanism to produce multiple thermal proton populations and beams locally in the solar wind

Lavraud, B., Kieokaew, R., Fargette, N., Louarn, P., Fedorov, A., André, N., Fruit, G., Génot, V., Réville, V., Rouillard, A. P., Plotnikov, I., Penou, E., Barthe, A., Prech, L., Owen, C. J., Bruno, R., Allegrini, F., Berthomier, M., Kataria, D., Livi, S., Raines, J. M., D’Amicis, R., Eastwood, J. P., Froment, C., Laker, R., Maksimovic, M., Marcucci, F., Perri, S., Perrone, D., Phan, T. D., Stansby, D., Stawarz, Julia, Toledo-Redondo, S., Vaivads, A., Verscharen, D., Zouganelis, I., Angelini, V., Evans, V., Horbury, T. S. and O’Brien, H. (2021) Magnetic reconnection as a mechanism to produce multiple thermal proton populations and beams locally in the solar wind. Astronomy & Astrophysics, 656. A37. ISSN 0004-6361

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Context. Spacecraft data revealed early on the frequent observation of multiple near-thermal proton populations in the solar wind. Decades of research on their origin have focused on processes such as magnetic reconnection in the low corona and wave-particle interactions in the corona and locally in the solar wind. Aims. This study aims to highlight the fact that such multiple thermal proton populations and beams are also produced by magnetic reconnection occurring locally in the solar wind. Methods. We used high-resolution Solar Orbiter proton velocity distribution function measurements, complemented by electron and magnetic field data, to analyze the association of multiple thermal proton populations and beams with magnetic reconnection during a period of slow Alfvénic solar wind on 16 July 2020. Results. At least six reconnecting current sheets with associated multiple thermal proton populations and beams, including a case of magnetic reconnection at a switchback boundary, were found on this day. This represents 2% of the measured distribution functions. We discuss how this proportion may be underestimated, and how it may depend on solar wind type and distance from the Sun. Conclusions. Although suggesting a likely small contribution, but which remains to be quantitatively assessed, Solar Orbiter observations show that magnetic reconnection must be considered as one of the mechanisms that produce multiple thermal proton populations and beams locally in the solar wind.

Item Type: Article
Additional Information: Funding Information: Acknowledgements. Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA. We thank all the ESA, NASA and instrument team members who made Solar Orbiter a success. We are grateful to the International Space Science Institute (ISSI) for its support of the team “Unravelling solar wind microphysics in the inner heliosphere” dedicated in part to the analysis of Solar Orbiter data. Work at LAB and IRAP was supported by CNES and CNRS. Solar Orbiter magnetometer operations are funded by the UK Space Agency (grant ST/T001062/1). T.S.H. and J.P.E. are supported by STFC grant ST/S000364/1. D.V. is supported by STFC Ernest Rutherford Fellowship ST/P003826/1 and STFC Consolidated Grant ST/S000240/1. L.P. was supported by the Czech Science Foundation, grant no. 19-18993S.
Uncontrolled Keywords: Solar wind, Sun: magnetic fields
Subjects: F300 Physics
F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 18 Jan 2023 15:57
Last Modified: 18 Jan 2023 16:00

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