Magnetospheric Conditions for STEVE and SAID: Particle Injection, Substorm Surge, and Field‐Aligned Currents
Magnetospheric Conditions for STEVE and SAID: Particle Injection, Substorm Surge, and Field‐Aligned Currents
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DOI：
10.1029/2020ja027782
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发表时间：
2020-08
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通讯作者：
Y. Nishimura;J. Yang;J. Weygand;W. Wang;B. Kosar;E. Donovan;V. Angelopoulos;L. Paxton;N. Nishitani
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作者：
Y. Nishimura;J. Yang;J. Weygand;W. Wang;B. Kosar;E. Donovan;V. Angelopoulos;L. Paxton;N. Nishitani
为了了解在亚暴恢复阶段导致热发射速度增强(STEAT)和亚极光离子漂移(SAID)的磁层-电离层条件，我们介绍了两个STEVE事件期间的亚暴极光、粒子注入和电流系统。这些事件被比作具有类似强度但没有史蒂夫的亚风暴事件。我们发现，有史蒂夫事件的亚风暴潮和强烈的上升流在黄昏达到，而非史蒂夫事件的亚风暴潮和强烈的上升流在午夜前后局部化。亚暴期间事件和大尺度相互作用的时间历史(THEMIS)卫星观测表明，Steve事件的粒子注入和快速等离子体片流动的位置也向黄昏移动。与非Steve事件相比，Steve事件的电子注入更强，离子注入更弱。在STEVE事件期间由超级双极光雷达网测量，但非STEVE事件只显示没有SAID的纬度宽的亚极光偏振流。为了解释观测结果，进行了午夜前和午夜注入的赖斯对流模式(RCM)模拟。模拟成功地解释了午夜前注入的电子较强、离子注入较弱以及SID的形成，这是因为注入的电子到达午夜前的内部磁层，并在离子和电子内部边界之间形成较窄的间隔。我们认为，亚暴和粒子注入向远离午夜黄昏的方向延伸，为创造史蒂夫提供了条件，因为更强的电子注入到午夜前。THEMIS全天成像仪网络确定史蒂夫弧东西长约1900公里(当地时间约2.5小时)，持续时间为1-1.5小时。
To understand magnetosphere‐ionosphere conditions that result in thermal emission velocity enhancement (STEVE) and subauroral ion drifts (SAID) during the substorm recovery phase, we present substorm aurora, particle injection, and current systems during two STEVE events. Those events are compared to substorm events with similar strength but without STEVE. We found that the substorm surge and intense upward currents for the events with STEVE reach the dusk, while those for the non‐STEVE substorms are localized around midnight. The Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations show that location of particle injection and fast plasma sheet flows for the STEVE events also shifts duskward. Electron injection is stronger and ion injection is weaker for the STEVE events compared to the non‐STEVE events. SAID are measured by Super Dual Auroral Radar Network during the STEVE events, but the non‐STEVE events only showed latitudinally wide subauroral polarization streams without SAID. To interpret the observations, Rice Convection Model (RCM) simulations with injection at premidnight and midnight have been conducted. The simulations successfully explain the stronger electron injection, weaker ion injection, and formation of SAID for injection at premidnight, because injected electrons reach the premidnight inner magnetosphere and form a narrower separation between the ion and electron inner boundaries. We suggest that substorms and particle injections extending far duskward away from midnight offer a condition for creating STEVE and SAID due to stronger electron injection to premidnight. The THEMIS all‐sky imager network identified the east‐west length of the STEVE arc to be ~1900 km (~2.5 h magnetic local time) and the duration to be 1–1.5 h.