Parker Solar Probe Observations of Solar Wind Energetic Proton Beams Produced by Magnetic Reconnection in the Near-Sun Heliospheric Current Sheet

T D Phan; J L Verniero; D Larson; B Lavraud; J F Drake; M Øieroset; J P Eastwood; S D Bale; R Livi; J S Halekas; P L Whittlesey; A Rahmati; D Stansby; M Pulupa; R J MacDowall; P A Szabo; A Koval; M Desai; S A Fuselier; M Velli; M Hesse; P S Pyakurel; K Maheshwari; J C Kasper; J M Stevens; A W Case; N E Raouafi

doi:10.1029/2021GL096986

Parker Solar Probe Observations of Solar Wind Energetic Proton Beams Produced by Magnetic Reconnection in the Near-Sun Heliospheric Current Sheet

Geophys Res Lett. 2022 May 16;49(9):e2021GL096986. doi: 10.1029/2021GL096986. Epub 2022 May 4.

Authors

T D Phan¹, J L Verniero², D Larson¹, B Lavraud^{3

4}, J F Drake⁵, M Øieroset¹, J P Eastwood⁶, S D Bale^{1

7}, R Livi¹, J S Halekas⁸, P L Whittlesey¹, A Rahmati¹, D Stansby⁹, M Pulupa¹, R J MacDowall², P A Szabo², A Koval^{2

10}, M Desai¹¹, S A Fuselier¹¹, M Velli¹², M Hesse¹³, P S Pyakurel¹, K Maheshwari¹, J C Kasper¹⁴, J M Stevens¹⁵, A W Case¹⁵, N E Raouafi¹⁶

Affiliations

¹ SSL University of California Berkeley CA USA.
² NASA Goddard Space Flight Center Greenbelt MD USA.
³ Laboratoire d'Astrophysique de Bordeaux University Bordeaux Pessac France.
⁴ IRAP CNRS CNES Université de Toulouse Toulouse France.
⁵ University of Maryland College Park MD USA.
⁶ The Blackett Laboratory Imperial College London London UK.
⁷ Physics Department University of California Berkeley CA USA.
⁸ University of Iowa Iowa City IA USA.
⁹ Mullard Space Science Laboratory University College London Dorking UK.
¹⁰ University of Maryland Baltimore County Baltimore MD USA.
¹¹ Southwest Research Institute San Antonio TX USA.
¹² University of California Los Angeles CA USA.
¹³ NASA Ames Research Center Moffett Field CA USA.
¹⁴ Climate and Space Sciences and Engineering University of Michigan Ann Arbor MI USA.
¹⁵ Smithsonian Astrophysical Observatory Cambridge MA USA.
¹⁶ Johns Hopkins University Applied Physics Laboratory Laurel MD USA.

Abstract

We report observations of reconnection exhausts in the Heliospheric Current Sheet (HCS) during Parker Solar Probe Encounters 08 and 07, at 16 R _s and 20 R _s , respectively. Heliospheric current sheet (HCS) reconnection accelerated protons to almost twice the solar wind speed and increased the proton core energy by a factor of ∼3, due to the Alfvén speed being comparable to the solar wind flow speed at these near-Sun distances. Furthermore, protons were energized to super-thermal energies. During E08, energized protons were found to have leaked out of the exhaust along separatrix field lines, appearing as field-aligned energetic proton beams in a broad region outside the HCS. Concurrent dropouts of strahl electrons, indicating disconnection from the Sun, provide further evidence for the HCS being the source of the beams. Around the HCS in E07, there were also proton beams but without electron strahl dropouts, indicating that their origin was not the local HCS reconnection exhaust.

Keywords: heliospheric current sheet; magnetic reconnection; parker solar probe; particle acceleration; solar wind.