The Heliospheric Current Sheet and Plasma Sheet during Parker Solar Probe's First Orbit

B. Lavraud (1) , N. Fargette , V. Reville (2) , A. Szabo (3) , J. Huang , A. Rouillard (4) , N. Viall , T. Phan (5) , J. Kasper (6) , S. Bale (7) , M. Berthomier (8) , J. Bonnell (8) , A. W Case , T. Dudok de Wit , J. P Eastwood , V. Genot (9) , K. Goetz (10) , L. S Griton (11) , J. Halekas (12) , P. Harvey , R. Kieokaew , K. Klein (13) , K. E Korreck (6) , A. Kouloumvakos , D. E Larson (8) , M. Lavarra (9) , R. Livi (14) , P. Louarn (1) , R. J Macdowall , M. Maksimovic (11) , D. Malaspina , T. Nieves-Chinchilla , R. F Pinto , N. Poirier (15) , M. Pulupa , N. E Raouafi , M. H. Stevens (16) , S. Toledo-Redondo (17) , P. L Whittlesey (7)

1 CESR - Centre d'étude spatiale des rayonnements
2 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
3 GSFC Laboratory for Extraterrestrial Physics
4 School of Physics and Astronomy [Southampton]
5 CPMOH - Centre de physique moléculaire optique et hertzienne
6 CfA - Harvard-Smithsonian Center for Astrophysics
7 UC Berkeley - University of California [Berkeley]
8 SSL - Space Sciences Laboratory [Berkeley]
9 IRAP - Institut de recherche en astrophysique et planétologie
10 School of Physics and Astronomy [Minneapolis]
11 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
12 Department of Physics and Astronomy [Iowa City]
13 GREGH - Groupement de Recherche et d'Etudes en Gestion à HEC
14 CNR - National Research Council of Italy | Consiglio Nazionale delle Ricerche
15 U1064 Inserm - CRTI - Centre de Recherche en Transplantation et Immunologie
16 NRL - Naval Research Laboratory
17 ESA - Agence Spatiale Européenne = European Space Agency

We present Heliospheric Current Sheet (HCS) and Plasma Sheet (HPS) observations during Parker Solar Probe's (PSP) first orbit around the Sun. We focus on the eight intervals that display a true sector boundary (TSB; based on suprathermal electron pitch angle distributions) with one or several associated current sheets. The analysis shows that (1) the main density enhancements in the vicinity of the TSB and HCS are typically associated with electron strahl dropouts, implying magnetic disconnection from the Sun, (2) the density enhancements are just about twice that in the surrounding regions, suggesting mixing of plasmas from each side of the HCS, (3) the velocity changes at the main boundaries are either correlated or anticorrelated with magnetic field changes, consistent with magnetic reconnection, (4) there often exists a layer of disconnected magnetic field just outside the high-density regions, in agreement with a reconnected topology, (5) while a few cases consist of short-lived density and velocity changes, compatible with short-duration reconnection exhausts, most events are much longer and show the presence of flux ropes interleaved with higher-β regions. These findings are consistent with the transient release of density blobs and flux ropes through sequential magnetic reconnection at the tip of the helmet streamer. The data also demonstrate that, at least during PSP's first orbit, the only structure that may be defined as the HPS is the density structure that results from magnetic reconnection, and its by-products, likely released near the tip of the helmet streamer.

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]

B. Lavraud, N. Fargette, V. Reville, A. Szabo, J. Huang, et al.. The Heliospheric Current Sheet and Plasma Sheet during Parker Solar Probe's First Orbit. The Astrophysical journal letters, 2020, 894 (2), pp.L19. ⟨10.3847/2041-8213/ab8d2d⟩. ⟨hal-02750279⟩