Steep plasma depletion in dayside polar cap during a CME-driven magnetic storm
Steep plasma depletion in dayside polar cap during a CME-driven magnetic storm
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在日冕物质抛射驱动的磁暴期间，日侧极冠中的等离子体急剧损耗
DOI：
10.1029/2012ja018138
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发表时间：
2013
影响因子：
--
通讯作者：
J. Sakai
中科院分区：
文献类型：
--
作者：
Okamoto;et al.;J. Sakai
2000年10月14日，通过EISCAT斯瓦尔巴德雷达（ESR）场向测量和北向低海拔测量，在电子密度高度增强的时间间隔内，在向阳面极冠中观察到一系列陡峭的等离子体耗尽。每次消耗开始时都从F2区高度的1013 × 1012 m − 3的增强水平急剧下降到1011 m − 3，并持续10-15分钟才恢复到增强水平。这些耗尽移动极的速度与观察到的离子漂移速度一致。DMSP航天器在包括这些事件间隔在内的较长一段时间内的观测表明，一个高离子密度区域从尖点的赤道方向一侧延伸到极冠，即，一个电离舌存在，离子密度非常低，在其prenoon一侧。太阳风观测表明，从IMFBy> 0到By < 0的急剧变化与ESR电子密度下降的每次出现有关。从这一前所未有的明确的相关性，我们提出了一个具体的方案：使用ESR观察到的一系列等离子体密度耗尽是电离舌的起伏边界向极漂移的结果;这种波动是在ESR观测之前大约20分钟通过方位侵入在尖点中产生的，响应于重连线足迹的快速午前移位，低密度等离子体的位置
A series of steep plasma depletions was observed in the dayside polar cap during an interval of highly enhanced electron density on 14 October 2000 through EISCAT Svalbard Radar (ESR) field‐aligned measurements and northward‐directed low‐elevation measurements. Each depletion started with a steep dropoff to as low as 1011m− 3from the enhanced level of ∼3 × 1012m−3at F2 region altitudes, and it continued for 10–15 min before returning to the enhanced level. These depletions moved poleward at a speed consistent with the observed ion drift velocity. DMSP spacecraft observations over an extended period of time which includes the interval of these events indicate that a region of high ion densities extended into the polar cap from the equatorward side of the cusp, i.e., a tongue of ionization existed, and that the ion densities were very low on its prenoon side. Solar wind observations show that a sharp change from IMFBy> 0 toBy< 0 is associated with each appearance of the ESR electron density dropoff. From this unprecedented clear correlation we present a specific scenario: the series of plasma density depletions observed using the ESR is a result of the poleward drift of the undulating boundary of the tongue of ionization; this undulation is created in the cusp roughly 20 min before the ESR observation by the azimuthal intrusion, in response to the rapid prenoon shift of the footprint of the reconnection line, of the low‐density plasmas originating in the morning sector.