Solar Wind Proton Heating and its Effect on Temperature Anisotropy Evolution between 0.05 and 1 au
Abstract
This study focuses on the radial evolution of the solar wind proton adiabatic invariants and temperature anisotropies in the inner heliosphere. More specifically, we study in-situ measurements provided by the Parker Solar Probe, between 0.05 au and 0.25 au from the Sun, and Solar Orbiter spacecraft between 0.3 au and 1 au. Throughout the studied range of radial distances, we observe a significant average heating in the direction perpendicular to the local magnetic field for both fast and slow solar wind populations. On the other hand, there is no clear deviation from adiabaticity in the parallel direction regardless of the wind speed. The perpendicular heating is enough to significantly reduce the generation of the temperature anisotropy expected from a double adiabatic evolution. Despite the heating, an important portion of the solar wind (especially the slower wind streams) develops substantial anisotropies with higher parallel temperatures, which eventually become constrained by kinetic firehose instabilities.
Related
- Solar-wind proton heating and its effect on the temperature anisotropy evolution between 0.05 and 1 au
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BibTeX
@misc{berriot2026solar,
title = {{Solar Wind Proton Heating and its Effect on Temperature Anisotropy Evolution between 0.05 and 1 au}},
author = {Etienne Berriot and Arnaud Zaslavsky and Olga Alexandrova and Pascal Démoulin and Petr Hellinger and Lorenzo Matteini},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.25824},
eprint = {2607.25824},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.25824},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Solar Wind Proton Heating and its Effect on Temperature Anisotropy Evolution between 0.05 and 1 au
AU - Etienne Berriot
AU - Arnaud Zaslavsky
AU - Olga Alexandrova
AU - Pascal Démoulin
AU - Petr Hellinger
AU - Lorenzo Matteini
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2607.25824
UR - https://arxiv.org/abs/2607.25824
AB - This study focuses on the radial evolution of the solar wind proton adiabatic invariants and temperature anisotropies in the inner heliosphere. More specifically, we study in-situ measurements provided by the Parker Solar Probe, between 0.05 au and 0.25 au from the Sun, and Solar Orbiter spacecraft between 0.3 au and 1 au. Throughout the studied range of radial distances, we observe a significant average heating in the direction perpendicular to the local magnetic field for both fast and slow solar wind populations. On the other hand, there is no clear deviation from adiabaticity in the parallel direction regardless of the wind speed. The perpendicular heating is enough to significantly reduce the generation of the temperature anisotropy expected from a double adiabatic evolution. Despite the heating, an important portion of the solar wind (especially the slower wind streams) develops substantial anisotropies with higher parallel temperatures, which eventually become constrained by kinetic firehose instabilities.
ER -