The geocoronal responses to the geomagnetic disturbances
The geocoronal responses to the geomagnetic disturbances
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DOI：
10.1002/2016ja023247
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发表时间：
2017-01-01
影响因子：
2.8
通讯作者：
Yoshikawa, I.
中科院分区：
文献类型：
--
作者：
Kuwabara, M.;Yoshioka, K.;Yoshikawa, I.
地球外逸层中的原子氢原子共振散射太阳莱曼α（121.6 nm）辐射，观察为氢地冕。散射太阳光子的测量使我们能够探测外层氢原子随时间变化的分布。带有极紫外光谱仪（EXTreme UV spectrosCope for ExosphEric Dynamics：EXCEED）的 Hisaki 卫星于 2013 年 9 月发射。EXCEED 从地球轨道获取行星大气/磁层的光谱图像（52-148 nm）。由于其轨道高度较低（约1000公里），该仪器拍摄的图像也包含地冕发射。在此背景下，自2013年以来，EXCEED提供了高时间分辨率（类似于1分钟）的地冕准连续遥感观测。这些观测提供了一个独特的数据库来确定外层密度结构的长期行为。在本文中，我们报告了 EXCEED 观测到的地磁扰动的外层结构响应。 2014年2月发生了几次Dst指数下降的地磁暴，地球夜间的莱曼α柱亮度突然暂时增加了约10%。 Hisaki透露，在暴风雨期间，磁活动峰值与莱曼α柱亮度变化之间的时间滞后约为2至6小时。为了解释观察结果，我们定量评估导致增加的因素。基于这些结果，外逸层和等离子体层之间通过电荷交换产生的耦合效应导致外逸层密度结构的变化。
Atomic hydrogen atoms in the terrestrial exosphere resonantly scatter solar Lyman alpha (121.6 nm) radiation, observed as the hydrogen geocorona. Measurements of scattered solar photons allow us to probe time-varying distributions of exospheric hydrogen atoms. The Hisaki satellite with the extreme ultraviolet spectrometer (EXtreme ultraviolet spectrosCope for ExosphEric Dynamics: EXCEED) was launched in September 2013. EXCEED acquires spectral images (52-148 nm) of the atmospheres/magnetospheres of planets from Earth orbit. Due to its low orbital altitude (similar to 1000 km), the images taken by the instrument also contain the geocoronal emissions. In this context, EXCEED has provided quasi-continuous remote sensing observations of the geocorona with high temporal resolution (similar to 1 min) since 2013. These observations provide a unique database to determine the long-term behavior of the exospheric density structure. In this paper, we report exospheric structural responses observed by EXCEED to geomagnetic disturbances. Several geomagnetic storms with decreases of Dst index occurred in February 2014 and the Lyman alpha column brightness on the night side of the Earth increased abruptly and temporarily by approximately 10%. Hisaki reveal that the time lag between the peaks of the magnetic activity and the changes in the Lyman alpha column brightness is found to be about 2 to 6h during storms. In order to interpret the observational results, we evaluate quantitatively the factors causing the increase. On the basis of these results, a coupling effect via charge exchange between the exosphere and plasmasphere causes variations of the exospheric density structure.