Changes in the Magnetic Field Topology and the Dayside/Nightside Reconnection Rates in Response to a Solar Wind Dynamic Pressure Front: A Case Study
Changes in the Magnetic Field Topology and the Dayside/Nightside Reconnection Rates in Response to a Solar Wind Dynamic Pressure Front: A Case Study
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DOI：
10.1029/2020ja028768
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
A. Boudouridis;H. Connor;D. Lummerzheim;A. Ridley;E. Zesta
中科院分区：
文献类型：
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作者：
A. Boudouridis;H. Connor;D. Lummerzheim;A. Ridley;E. Zesta
与太阳风动压（PSW）急剧增强相关的最重要观测之一是极光椭圆向极扩展和极帽关闭。极帽收缩在很宽的范围内的磁本地时间（MLT），在与电离层对流和transpolar电位的观察到的增加，导致的结论是，nightside重联率显着增强后，压力前的影响。然而，这种增强的尾部重连从未被直接测量过。我们证明了太阳风动压锋对极冠闭合的影响，并首次测量了磁尾增强的重联率，发生在向南的背景行星际磁场（IMF）条件下的情况。利用极区紫外成像仪（UVI）探测开闭磁力线边界的位置，结合联合收割机和AMIE电位同化映射，计算沿着极冠边界的电离层电场，从而估算昼侧/夜侧重联率的变化。我们发现在所有可用的MLT的极帽边界的强烈响应，表现出显着减少的开放通量内容。我们还观察到一个即时响应的昼侧重连率，加上一个阶段性的反应，延迟了15-20分钟，夜侧重连率。最后，我们提供的观测结果与开放地球空间大气环流模型（OpenGGCM）的结果进行比较，阐明显着的协议和分歧。
One of the most significant observations associated with a sharp enhancement in solar wind dynamic pressure, PSW , is the poleward expansion of the auroral oval and the closing of the polar cap. The polar cap shrinking over a wide range of magnetic local times (MLTs), in connection with an observed increase in ionospheric convection and the transpolar potential, led to the conclusion that the nightside reconnection rate is significantly enhanced after a pressure front impact. However, this enhanced tail reconnection has never been directly measured. We demonstrate the effect of a solar wind dynamic pressure front on the polar cap closure, and for the first time, measure the enhanced reconnection rate in the magnetotail, for a case occurring during southward background Interplanetary Magnetic Field (IMF) conditions. We use Polar Ultra‐Violet Imager (UVI) measurements to detect the location of the open‐closed field line boundary, and combine them with Assimilative Mapping of Ionospheric Electrodynamics (AMIE) potentials to calculate the ionospheric electric field along the polar cap boundary, and thus evaluate the variation of the dayside/nightside reconnection rates. We find a strong response of the polar cap boundary at all available MLTs, exhibiting a significant reduction of the open flux content. We also observe an immediate response of the dayside reconnection rate, plus a phased response, delayed by ∼15–20 min, of the nightside reconnection rate. Finally, we provide comparison of the observations with the results of the Open Geospace General Circulation Model (OpenGGCM), elucidating significant agreements and disagreements.