The Radial Evolution of the Solar Wind as Organized by Electron Distribution Parameters

J. Halekas; P. Whittlesey; D. Larson; M. Maksimovic; R. Livi; M. Berthomier; J. Kasper; A. Case; M. Stevens; S. Bale; R. Macdowall; M. Pulupa

doi:10.3847/1538-4357/ac85b8

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The Radial Evolution of the Solar Wind as Organized by Electron Distribution Parameters

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The Radial Evolution of the Solar Wind as Organized by Electron Distribution Parameters

J. Halekas, P. Whittlesey, D. Larson, M. Maksimovic, R. Livi, M. Berthomier, J. Kasper, A. Case, M. Stevens, S. Bale, …

The Astrophysical journal, Vol.936(1), p.53

09/01/2022

DOI: 10.3847/1538-4357/ac85b8

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Abstract

Abstract We utilize observations from the Parker Solar Probe (PSP) to study the radial evolution of the solar wind in the inner heliosphere. We analyze electron velocity distribution functions observed by the Solar Wind Electrons, Alphas, and Protons suite to estimate the coronal electron temperature and the local electric potential in the solar wind. From the latter value and the local flow speed, we compute the asymptotic solar wind speed. We group the PSP observations by asymptotic speed, and characterize the radial evolution of the wind speed, electron temperature, and electric potential within each group. In agreement with previous work, we find that the electron temperature (both local and coronal) and the electric potential are anticorrelated with wind speed. This implies that the electron thermal pressure and the associated electric field can provide more net acceleration in the slow wind than in the fast wind. We then utilize the inferred coronal temperature and the extrapolated electric + gravitational potential to show that both electric field driven exospheric models and the equivalent thermally driven hydrodynamic models can explain the entire observed speed of the slowest solar wind streams. On the other hand, neither class of model can explain the observed speed of the faster solar wind streams, which thus require additional acceleration mechanisms.

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Title: Subtitle: The Radial Evolution of the Solar Wind as Organized by Electron Distribution Parameters
Creators: J. Halekas - University of Iowa
P. Whittlesey - University of California, Berkeley
D. Larson - University of California, Berkeley
M. Maksimovic - Université Paris Cité
R. Livi - University of California, Berkeley
M. Berthomier - Laboratoire de Physique des Plasmas
J. Kasper - 1366 Technologies (United States)
A. Case - Smithsonian Astrophysical Observatory
M. Stevens - Smithsonian Astrophysical Observatory
S. Bale - University of California, Berkeley
R. Macdowall - Goddard Space Flight Center
M. Pulupa - University of California, Berkeley
Resource Type: Journal article
Publication Details: The Astrophysical journal, Vol.936(1), p.53
DOI: 10.3847/1538-4357/ac85b8
ISSN: 0004-637X
eISSN: 1538-4357
Publisher: American Astronomical Society
Grant note: DOI: 10.13039/100000104, name: National Aeronautics and Space Administration, award: NNN06AA01C
Language: English
Date published: 09/01/2022
Academic Unit: Physics and Astronomy
Record Identifier: 9984428798402771

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