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Proton Temperature Anisotropy across Interplanetary Shocks: A Statistical Analysis with WIND Observations

delete2026-05-10
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PRE
AI
J
Jin, Zeping
L
Lingling Zhao *
X
Xingyu Zhu
V
V. Florinski
G
G. P. Zank
J
J. A. le Roux
Y
Yiming Jiao
A
Ashok Silwal
S
Subashchandar, Nibuna S. M.
DOI:10.3847/2041-8213/ae6067delete
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Abstract

Abstract

En 中文
Interplanetary (IP) shocks efficiently modify the proton temperature anisotropy of the solar wind. Analyzing similar to 800 IP shocks observed by the Wind spacecraft from 1997 to 2024, we present a statistical study of upstream and downstream proton temperature anisotropy and its dependence on shock geometry, compression, and distance from the shock. We find that (1) quasi-perpendicular shocks produce a pronounced enhancement of perpendicular temperature downstream (T-perpendicular to > T-parallel to), whereas parallel shocks remain near isotropic downstream due to typically stronger upstream T-parallel to; (2) comparisons with the Chew-Goldberger-Low (CGL) double-adiabatic model reveal geometry-dependent deviations, as CGL overestimates downstream perpendicular heating and underestimates parallel heating at quasi-perpendicular shocks, with the opposite trend at quasi-parallel shocks, highlighting the importance of nonadiabatic processes beyond simple compression; (3) shock-driven anisotropy is strongly localized near the shock and gradually relaxes toward typical solar wind conditions farther downstream as the shock's influence diminishes; and (4) downstream anisotropy is regulated by kinetic instabilities, with quasi-perpendicular shocks constrained by proton cyclotron and mirror instabilities and quasi-parallel shocks limited by the parallel fire-hose instability. Together, these results show that the evolution of temperature anisotropy at IP shocks is controlled by shock geometry, localized processes, and instability-driven regulation.
Keywords:
PARTICLE-ACCELERATION
JUMP CONDITIONS
PLASMA
WAVES
FLUX
MAGNETOSHEATH
FLUCTUATIONS
TURBULENCE
MHD

Journal

Astrophysical Journal Letters cover
Astrophysical Journal Letters
IF:
11.7
Papers:
1.2W
Citations:
5.9W

Organization

University of Alabama System cover
University of Alabama System
Scholars:
4.2W
Papers: 3.7W
Citations: 68
U
university of alabama huntsville
Scholars:
1.8K
Papers: 1.5K
Citations: 0
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