火星+E半球地壳磁异常下游的开尔文-亥姆霍兹涡旋

中文摘要 AI 辅助

在无磁场的行星天体上，太阳风边界处的开尔文-亥姆霍兹（KH）不稳定性是大气逃逸的关键驱动因素，从根本上塑造了长期气候演化。这种由剪切驱动的等离子体混合在理论上被预测为不对称的，强烈偏向于太阳风电场指向行星的半球（-E半球）。本文利用MAVEN就地测量数据，报告了在传统上不利的火星+E半球观测到的一列连贯的充分发展的KH涡旋。来自天问一号的同时期上游约束证实了稳定的行星际磁场，表明持续剪切驱动的增长而非瞬态边界响应。我们发现这些涡旋在强南部地壳磁异常下游的膨胀的弱场边界层内发展。我们的分析表明，区域边界结构可以超越大尺度半球偏好，促进局部KH增长。这些发现证明剪切驱动的逃逸路径可以在传统不利区域运行，改变了我们对弱磁化行星大气挥发性物质损失的理解。

英文摘要

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.

发表机构

• University of Science and Technology of China（中国科学技术大学）
• The University of Hong Kong（香港大学）
• National Space Science Center, Chinese Academy of Sciences（中国科学院国家空间科学中心）
• Harbin Institute of Technology, Shenzhen（哈尔滨工业大学（深圳））
• Space Research Institute, Austrian Academy of Sciences（奥地利科学院空间研究所）

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