Issue |
A&A
Volume 676, August 2023
|
|
---|---|---|
Article Number | A137 | |
Number of page(s) | 6 | |
Section | The Sun and the Heliosphere | |
DOI | https://doi.org/10.1051/0004-6361/202346815 | |
Published online | 23 August 2023 |
Distribution of alpha temperature anisotropy in the slow and fast solar wind: WIND observations and Vlasov theory
1
Institute of Space Physics, Luoyang Normal University, 471934 Luoyang, PR China
e-mail: fenghq9921@163.com
2
Henan Key Laboratory of Electromagnetic Transformation and Detection, Luoyang Normal University, 471934 Luoyang, PR China
3
School of Physics and Electronics, Hunan Normal University, 410081 Changsha, PR China
4
Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, 210034 Nanjing, PR China
Received:
4
May
2023
Accepted:
7
July
2023
Context. Alpha particles in the solar wind frequently show temperature anisotropies, which can be constrained by various kinetic instabilities. However, the detailed constraint mechanism remains unclear, especially in different types of solar wind.
Aims. Using data obtained by the Wind spacecraft between 2005 and 2015, we investigate the distribution of alpha temperature anisotropy and the correlation with background plasma parameters in the slow and fast solar wind.
Methods. We present a comparison between observations of the alpha temperature anisotropy by the Wind spacecraft and theoretical results obtained with the linear Vlasov theory.
Results. The results show that the distribution of the alpha temperature anisotropy depends not only on the parallel temperature ratio of alpha to proton Tα∥/Tp∥ and the proton temperature anisotropy Tp⊥/Tp∥, but also on the drift velocity of alpha to proton vα/vA and the solar wind velocity vsw. In particular, there are clearly different constraining mechanisms on the distribution of alpha temperature anisotropy in the slow and fast solar wind.
Conclusions. The alpha temperature anisotropy instability together with different types of free energy can be effective for regulating the alpha temperature anisotropy in the slow and fast solar wind.
Key words: waves / instabilities / solar wind / magnetohydrodynamics (MHD)
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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