MESSENGER X-ray observations of magnetosphere-surface interaction on the nightside of Mercury
MESSENGER X-ray observations of magnetosphere-surface interaction on the nightside of Mercury
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DOI：
10.1016/j.pss.2016.03.005
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发表时间：
2016-06-01
影响因子：
2.4
通讯作者：
Yeoman, T. K.
中科院分区：
文献类型：
--
作者：
Lindsay, S. T.;James, M. K.;Yeoman, T. K.
最近完成的信使号水星任务探测到了这颗行星黑夜表面的X射线荧光事件，这是由电子的沉淀引起的。我们扩展了以前报道的此类事件的星表，使用基于元素荧光线的过滤器来构建一个涵盖信使任务全部五年的星表。我们发现，大多数事件的位置是在行星黎明侧的两个明显的纬度带上排序的，中心位置类似于北纬50度和北纬20度。这意味着电子降水要么是稳定的，要么在长达几分钟的时间尺度上重复发生，与水星磁球环境的特征时间有关。相反，只有40%的信使轨道上观察到了X射线荧光事件，尽管我们注意到一些事件在过滤过程中不可避免地会丢失。我们认为，降水最强烈的区域由表面上相关磁场线足迹的位置决定。我们能够根据观察到的X射线光谱中的荧光线，对以这种方式沉淀的电子的能量施加推测限制。发现最强降水区域的极地边界与开闭场线边界配置在一起。我们使用磁场模型来追踪从这些荧光点到磁尾中隐含的起源位置的场线。(C)2016年提交人。由爱思唯尔有限公司出版。这是一篇在CC许可下的开放获取文章。
The recently completed MESSENGER mission to Mercury has detected X-ray fluorescence events on the nightside surface of the planet, induced by the precipitation of electrons. We expand upon previously reported catalogues of such events, using a filter based on elemental fluorescence lines to construct a catalogue covering the full five years of the MESSENGER mission. We find that the locations of the majority of these events are ordered in two clear latitudinal bands on the dawn side of the planet centred at similar to 50 degrees N and similar to 20 degrees S. Electron precipitation is implied to be either stable or occurring repeatedly on timescales of up to several minutes, long in relation to characteristic times of the Mercury magneto spheric environment. Conversely, X-ray fluorescence events are observed on only similar to 40% of MESSENGER orbits, although we note that some events are inevitably lost during the filtering process. We suggest that the regions of most intense precipitation are determined by the location of the relevant magnetic field line footprints on the surface. We are able to place speculative limits on the energies of electrons precipitating in this manner based on fluorescence lines in the observed X-ray spectra. The poleward boundaries of the regions of most intense precipitation are found to be collocated with the open-closed field line boundary. We use a magnetic field model to trace field lines from these fluorescence sites to implied locations of origin in the magnetotail. (C) 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.