Kelvin-Helmholtz vortices in the Martian +E hemisphere downstream of crustal magnetic anomalies
Abstract
At unmagnetized planetary bodies, the Kelvin-Helmholtz (KH) instability at the solar-wind boundary is a key driver of atmospheric escape, fundamentally shaping long-term climate evolution. This shear-driven plasma mixing is theoretically predicted to be asymmetric, strongly favoring the hemisphere where the solar-wind electric field points toward the planet (-E hemisphere). Here we report the observation of a coherent train of fully developed KH vortices in the traditionally unfavorable +E hemisphere of Mars, using in-situ MAVEN measurements. Contemporaneous upstream constraints from Tianwen-1 confirm a steady interplanetary magnetic field, indicating sustained shear-driven growth rather than a transient boundary response. We find that these vortices developed within an expanded, weak-field boundary layer downstream of strong southern crustal magnetic anomalies. Our analysis suggests that regional boundary structuring can override the large-scale hemispheric preference to facilitate localized KH growth. These findings demonstrate that shear-driven escape pathways can operate in traditionally unfavorable regions, altering our understanding of atmospheric volatile loss at weakly magnetized planets.
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BibTeX
@misc{niu2026kelvinhelmholtz,
title = {{Kelvin-Helmholtz vortices in the Martian +E hemisphere downstream of crustal magnetic anomalies}},
author = {Junxi Niu and Tong Dang and Jiuhou Lei and Binzheng Zhang and Wenya Li and Binbin Tang and Junjie Chen and Sudong Xiao and Tielong Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.27474},
eprint = {2609.27474},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.27474},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Kelvin-Helmholtz vortices in the Martian +E hemisphere downstream of crustal magnetic anomalies
AU - Junxi Niu
AU - Tong Dang
AU - Jiuhou Lei
AU - Binzheng Zhang
AU - Wenya Li
AU - Binbin Tang
AU - Junjie Chen
AU - Sudong Xiao
AU - Tielong Zhang
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2609.27474
UR - https://arxiv.org/abs/2609.27474
AB - At unmagnetized planetary bodies, the Kelvin-Helmholtz (KH) instability at the solar-wind boundary is a key driver of atmospheric escape, fundamentally shaping long-term climate evolution. This shear-driven plasma mixing is theoretically predicted to be asymmetric, strongly favoring the hemisphere where the solar-wind electric field points toward the planet (-E hemisphere). Here we report the observation of a coherent train of fully developed KH vortices in the traditionally unfavorable +E hemisphere of Mars, using in-situ MAVEN measurements. Contemporaneous upstream constraints from Tianwen-1 confirm a steady interplanetary magnetic field, indicating sustained shear-driven growth rather than a transient boundary response. We find that these vortices developed within an expanded, weak-field boundary layer downstream of strong southern crustal magnetic anomalies. Our analysis suggests that regional boundary structuring can override the large-scale hemispheric preference to facilitate localized KH growth. These findings demonstrate that shear-driven escape pathways can operate in traditionally unfavorable regions, altering our understanding of atmospheric volatile loss at weakly magnetized planets.
ER -