Solar wind energy flux observations in the inner heliosphere: first results from Parker Solar Probe

M. Liu (1) , K. Issautier (1) , N. Meyer-Vernet (1) , M. Moncuquet (1) , M. Maksimovic (1) , J. S Halekas (2) , J. Huang (3) , L. Griton (4) , S. Bale (5, 6, 7, 8) , J. W Bonnell (5) , A. W Case (9) , K. Goetz (10) , P. R Harvey (5) , J. C Kasper (3, 9) , R. J Macdowall (11) , D. M Malaspina (12) , M. Pulupa (5) , M. L Stevens (9)

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
2 Department of Physics and Astronomy [Iowa City]
3 CLaSP - Department of Climate and Space Sciences and Engineering
4 IRAP - Institut de recherche en astrophysique et planétologie
5 SSL - Space Sciences Laboratory [Berkeley]
6 QMUL - Queen Mary University of London
7 Imperial College London
8 UC Berkeley - University of California [Berkeley]
9 Smithsonian Astrophysical Observatory
10 UMN - University of Minnesota System
11 GSFC - NASA Goddard Space Flight Center
12 University of Colorado [Boulder]

Aims. We investigate the solar wind energy flux in the inner heliosphere using 12-day observations around each perihelion of Encounter One (E01), Two (E02), Four (E04), and Five (E05) of Parker Solar Probe (PSP), respectively, with a minimum heliocentric distance of 27.8 solar radii (R⊙). Methods. Energy flux was calculated based on electron parameters (density ne, core electron temperature Tc, and suprathermal electron temperature Th) obtained from the simplified analysis of the plasma quasi-thermal noise (QTN) spectrum measured by RFS/FIELDS and the bulk proton parameters (bulk speed Vp and temperature Tp) measured by the Faraday Cup onboard PSP, SPC/SWEAP. Results. Combining observations from E01, E02, E04, and E05, the averaged energy flux value normalized to 1 R⊙ plus the energy necessary to overcome the solar gravitation (WR⊙) is about 70 ± 14 W m−2, which is similar to the average value (79 ± 18 W m−2) derived by Le Chat, G., Issautier, K., & Meyer-Vernet, N. (2012, Sol. Phys., 279, 197) from 24-yr observations by Helios, Ulysses, and Wind at various distances and heliolatitudes. It is remarkable that the distributions of WR⊙ are nearly symmetrical and well fitted by Gaussians, much more so than at 1 AU, which may imply that the small heliocentric distance limits the interactions with transient plasma structures.

Mots clés: solar wind; Sun: heliosphere; Sun: corona; Sun: fundamental parameters; plasmas; acceleration of particles

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

M. Liu, K. Issautier, N. Meyer-Vernet, M. Moncuquet, M. Maksimovic, et al.. Solar wind energy flux observations in the inner heliosphere: first results from Parker Solar Probe. Astronomy and Astrophysics - A&A, 2021, 650, pp.A14. ⟨10.1051/0004-6361/202039615⟩. ⟨hal-03266168⟩