Direct Observations of a Polar Cap Patch Formation Associated With Dayside Reconnection Driven Fast Flow
Direct Observations of a Polar Cap Patch Formation Associated With Dayside Reconnection Driven Fast Flow
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直接观察与白天重新连接驱动的快速流相关的极帽斑块形成
DOI：
10.1029/2019ja027745
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
M. Ruohoniemi
中科院分区：
文献类型：
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作者：
Jiaen Ren;S. Zou;E. Kendall;A. Coster;K. Sterne;M. Ruohoniemi
在地磁扰动期间，向阳面太阳产生的浓缩F区等离子体可以从中纬度地区传输到极冠，产生像极冠斑块一样的等离子体密度不规则性，这可能导致闪烁并降低极纬卫星通信和导航的性能。本文对2016年10月13日强磁暴期间极冠斑块的动态形成过程进行了观测和研究。在风暴主相期间，风暴增强密度（SED）是在一段较长时间的强南向行星际磁场（IMF）Bz条件下形成的。总电子含量（TEC）图显示，一个极地帽补丁分割从SED羽。Sondrestrom非相干散射雷达（ISR）位于分割区域的正下方，捕捉到了动态过程。结果表明，斑块的分割与向阳面尖点入流区附近东北气流的突然增强有关，增强速度约为2km/s。观察到沿着的流动浪涌与突然E区电子温度升高，F区离子温度升高，密度下降。上游太阳风和IMF观测表明，流动增强与突然和短期的IMF负漂移触发的向阳面磁场重联有关。定量估计表明，等离子体密度损失，由于增强摩擦加热是不够的补丁分割，因为升高的F区密度峰值在~500公里的解离重组效率低下。相反，通过从当地时间较早的快速流动通道输送的低密度血浆将贴片与SED分割。
Dayside solar‐produced concentrated F region plasma can be transported from the midlatitude region into the polar cap during geomagnetically disturbed period, creating plasma density irregularities like polar cap patches, which can cause scintillation and degrade performance of satellite communication and navigation at polar latitudes. In this paper, we observed and investigated a dynamic formation process of a polar cap patch during the 13 October 2016 intense geomagnetic storm. During the storm main phase, storm‐enhanced density (SED) was formed within an extended period of strong southward interplanetary magnetic field (IMF) Bz condition. Total electron content (TEC) map shows that a polar cap patch was segmented from the SED plume. The Sondrestrom Incoherent Scatter Radar (ISR) was right underneath the segmentation region and captured the dynamic process. It shows that the patch segmentation was related with a sudden northeastward flow enhancement reaching ~2 km/s near the dayside cusp inflow region. The flow surge was observed along with abrupt E region electron temperature increase, F region ion temperature increase, and density decrease. The upstream solar wind and IMF observations suggest that the flow enhancement was associated with dayside magnetic reconnection triggered by a sudden and short period of IMF By negative excursion. Quantitative estimation suggests that plasma density loss due to enhanced frictional heating was insufficient for the patch segmentation because the elevated F region density peaking at ~500 km made dissociative recombination inefficient. Instead, the patch was segmented from the SED by low‐density plasma transported by the fast flow channel from earlier local time.