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.

中文翻译：

---

STEVE和SAID的磁层条件：粒子注入，亚暴浪涌和场对准电流

为了了解在亚暴恢复阶段导致热发射速度提高（STEVE）和极光下离子漂移（SAID）的磁层-电离层条件，我们介绍了两次STEVE事件期间的亚暴极光，粒子注入和当前系统。将这些事件与强度类似但没有STEVE的亚暴事件进行比较。我们发现，STEVE事件的亚暴浪潮和强烈的上升气流到达黄昏，而非STEVE亚暴的浪潮则集中在午夜左右。事件和亚暴期间宏观尺度相互作用的时间历史（THEMIS）卫星观测结果表明，STEVE事件的粒子注入和快速等离子流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，而离子注入的能力较弱。SAID是在STEVE事件期间由超级双极光雷达网络测量的，但非STEVE事件仅显示了横向宽的极光亚极化波，而没有SAID。为了解释这些观察结果，已经进行了在午夜和午夜注入的水稻对流模型（RCM）模拟。该模拟成功地解释了更强的电子注入，较弱的离子注入以及在午夜之前注入的SAID的形成，因为注入的电子到达午夜之前的内部磁层，并在离子和电子内部边界之间形成了较窄的间隔。我们建议亚暴雨和粒子注入距离午夜很远，这是由于到午夜之前较强的电子注入为创造STEVE和SAID提供了条件。THEMIS全天候影像网络确定STEVE弧的东西向长度为〜1900 km（磁性本地时间为〜2.5 h），持续时间为1-1.5 h。