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Title: Regulation of Solar Wind Electron Temperature Anisotropy by Collisions and Instabilities

Journal Article · · The Astrophysical Journal

Abstract Typical solar wind electrons are modeled as being composed of a dense but less energetic thermal “core” population plus a tenuous but energetic “halo” population with varying degrees of temperature anisotropies for both species. In this paper, we seek a fundamental explanation of how these solar wind core and halo electron temperature anisotropies are regulated by combined effects of collisions and instability excitations. The observed solar wind core/halo electron data in ( β , T / T ) phase space show that their respective occurrence distributions are confined within an area enclosed by outer boundaries. Here, T / T is the ratio of perpendicular and parallel temperatures and β is the ratio of parallel thermal energy to background magnetic field energy. While it is known that the boundary on the high- β side is constrained by the temperature anisotropy-driven plasma instability threshold conditions, the low- β boundary remains largely unexplained. The present paper provides a baseline explanation for the low- β boundary based upon the collisional relaxation process. By combining the instability and collisional dynamics it is shown that the observed distribution of the solar wind electrons in the ( β , T / T ) phase space is adequately explained, both for the “core” and “halo” components.

Sponsoring Organization:
USDOE
Grant/Contract Number:
SC0022963
OSTI ID:
2475434
Journal Information:
The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 975; ISSN 0004-637X
Publisher:
American Astronomical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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