Switchbacks in the Young Solar Wind: Electron Evolution Observed inside Switchbacks between 0.125 au and 0.25 au

Raaman Nair (1) , Jasper Halekas (1) , Phyllis Whittlesey (2) , Davin Larson (2) , Roberto Livi (2) , Matthieu Berthomier (3) , Justin Kasper (4) , Anthony Case (5) , Michael Stevens (6) , Stuart Bale (2) , Robert Macdowall (7) , Marc Pulupa (2)

1 Department of Physics and Astronomy, University of Iowa
2 SSL - Space Sciences Laboratory [Berkeley]
3 LPP - Laboratoire de Physique des Plasmas
4 Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109, USA
5 CfA - Harvard-Smithsonian Center for Astrophysics
6 Smithsonian Astrophysical Observatory
7 GSFC Laboratory for Extraterrestrial Physics

Switchbacks are localized deviations from the nominal Parker spiral field in the solar wind. In this study, we investigate the electron distributions inside switchbacks, focusing primarily on the suprathermal (halo and strahl) populations. We explore electron parameters in relation to the angle of rotation of the magnetic field from radial to determine whether electron distributions observed within switchbacks have any differences from those outside of switchbacks. Our observations reveal several trends in the suprathermal electron populations inside switchbacks. We find that the sunward deficit in the electron velocity distribution function typically observed near the Sun is filled in at larger rotation angles. This results in the suprathermal electron density and heat flux in the antistrahl direction changing from a negative to a positive value. On many days, we also observe a positive correlation between the halo density and rotation angle, and this may suggest that the growth of the halo may fill in the sunward deficit. We also find that strahl distributions have an increased average angular spread at large magnetic field rotation angles. The increase in suprathermal electron flux in the antistrahl direction, and the increase in strahl width, together could suggest that enhanced scattering occurs inside switchbacks. Electron core beta values tend to increase with the magnetic field rotation angle, mainly due to a decrease in magnetic pressure. An increase in electron beta may favor the growth of instabilities inside switchbacks. The Parker Solar Probe observations therefore support an enhanced role for wave–particle interactions in switchbacks.

Domaines: Planète et Univers [physics]

Raaman Nair, Jasper Halekas, Phyllis Whittlesey, Davin Larson, Roberto Livi, et al.. Switchbacks in the Young Solar Wind: Electron Evolution Observed inside Switchbacks between 0.125 au and 0.25 au. The Astrophysical Journal, 2022, 936 (2), pp.164. ⟨10.3847/1538-4357/ac88c4⟩. ⟨hal-04306023⟩