Mercury's three‐dimensional asymmetric magnetopause
Mercury's three‐dimensional asymmetric magnetopause
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DOI：
10.1002/2015ja021425
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发表时间：
2015-09
期刊：
影响因子：
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通讯作者：
J. Zhong;W. Wan;J. Slavin;Y. Wei;R. Lin;L. Chai;J. Raines;Z. Rong;X. H. Han
中科院分区：
文献类型：
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作者：
J. Zhong;W. Wan;J. Slavin;Y. Wei;R. Lin;L. Chai;J. Raines;Z. Rong;X. H. Han
水星的磁层顶在太阳系中是独一无二的，因为它的体积相对较小，而且离太阳很近。基于3年来水星表面、空间环境、地球化学、测距轨道磁强计和快速成像等离子体光谱仪的数据，确定了总共5694次经过的平均磁层顶位置。我们将这些磁层顶位置拟合为三维非轴对称磁层顶，其中包括已成功应用于地球的尖端区域的凹痕。我们的模型预测水星的磁层顶在尖端周围高度凹陷，中心深度约为0.64 RM，白天延伸很大。因此，日侧极地磁层顶维数小于赤道磁层顶维数。在垂直于水星-太阳线的平面上，白天侧磁层顶的横截面沿着黎明-黄昏方向被延长和拉长。相反，在水星下游1.5 RM处，终止面下游的磁层顶在南北方向比东西方向大2.6 RM到2.2 RM。由于内部偶极子向北偏移，该模型预测太阳风可以直接进入位于南半球中磁纬度的水星表面。在极高的太阳风压力条件下，北半球中磁纬也可能受到太阳风的直接影响。
Mercury's magnetopause is unique in the solar system due to its relatively small size and its close proximity to the Sun. Based on 3 years of MErcury Surface, Space ENvironment, GEochemistry, and Ranging orbital Magnetometer and the Fast Imaging Plasma Spectrometer data, the mean magnetopause location was determined for a total of 5694 passes. We fit these magnetopause locations to a three‐dimensional nonaxially symmetric magnetopause which includes an indentation for the cusp region that has been successfully applied to the Earth. Our model predicts that Mercury's magnetopause is highly indented surrounding the cusp with central depth ~0.64 RM and large dayside extension. The dayside polar magnetopause dimension is, thus, smaller than the equatorial magnetopause dimension. Cross sections of the dayside magnetopause in planes perpendicular to the Mercury‐Sun line are prolate and elongated along the dawn‐dusk direction. In contrast, the magnetopause downstream of the terminator plane is larger in the north‐south than the east‐west directions by a ratio of 2.6 RM to 2.2 RM at a distance of 1.5 RM downstream of Mercury. Due to the northward offset of the internal dipole, the model predicts that solar wind has direct access to the surface of Mercury at middle magnetic latitudes in the southern hemisphere. During extremely high solar wind pressure conditions, the northern hemisphere middle magnetic latitudes may also be subject to direct solar wind impact.