Explosive energy release in space plasmas: unravelling the magnetospheric dynamics of substorms

亚暴是一种常见的空间天气扰动，包括夜面极光的迅速增强、地面磁扰动、环电流和辐射带的增强以及磁层外等离子体的加热。亚暴在30分钟内释放出约1 PJ（1015 J）的能量，其中大约一半的能量被倾倒到大气中。在标准亚暴模型中，亚暴有三个阶段：一个约1小时的增长阶段，在此期间，磁层和太阳风之间的重新连接将能量添加到地球的磁尾;膨胀阶段持续约20分钟，其中一些能量迅速释放，创造明亮的极光并重新配置地球的磁场;以及持续1-2小时的恢复阶段，在该恢复阶段期间能量继续释放，但是以降低的速率释放，并且系统开始返回到预处理阶段。亚暴状态。地球磁尾磁场通过重连重新配置是亚暴周期的关键组成部分。研究表明，重联爆发的特征是亚暴周期的一个关键组成部分，并可能通过系统输送大量的磁通量。它们也被推断为引发亚暴活动的关键部分（所谓的亚暴引发的“由外向内”模型）。然而，最近的研究表明，亚暴膨胀阶段的初始特征是内磁层的等离子体不稳定性，不需要首先启动重连。鉴于重连被认为是全球亚暴活动的一个关键组成部分，这使得不稳定性的开始和磁场的重新配置之间存在明显的脱节。本项目旨在提高我们对磁层内亚暴过程的理解，将重连、磁尾重新配置和等离子体不稳定性的特征观测放在相对的背景下：（i）比较不同的现场和远距离探测亚暴特征的相对时间，包括磁层快速流动和超低频波增长;（ii）确定哪些观测特征是所有亚暴共有的，并研究是否存在非共有特征的影响;（iii）研究亚暴和非亚暴活动期间“亚暴特征”的发生和影响。该项目将涉及检查各种数据源，包括来自星团、THEMIS和MMS以及来自磁强计链和极光全天空相机的地面数据。

The substorm is a common space weather disturbance, which includes a rapid enhancement in the nightside aurora, magnetic disturbances on the ground, enhancements in the ring current and radiation belts and heating of plasma further out in the magnetosphere. Substorms release ~1 PJ (1015 J) of energy in ~30 min, with approximately half of this energy being dumped into the atmosphere. This energy release and the processes associated with it have the potential to be harmful to technology in space and on the ground, making substorms a key component of space weather.In the standard substorm model, substorms have three phases: a growth phase of ~1 hour during which reconnection between the magnetosphere and the solar wind adds energy into Earth's magnetotail; an expansion phase lasting ~20 min in which some of this energy is rapidly released, creating bright aurora and reconfiguring Earth's magnetic field; and a recovery phase that lasts 1-2 hours during which energy continues to be released but at a decreasing rate and the system begins to return to the pre-substorm state.The reconfiguration of Earth's magnetotail magnetic field by reconnection is a key component of the substorm cycle. Studies have shown that signatures of bursts of reconnection are a key component of the substorm cycle and may transport significant amounts of magnetic flux through the system. They have also been inferred to be a key part in initiating the substorm activity (the so-called 'outside-in' model of substorm initiation). However, recent studies have shown that the initial signatures of the substorm expansion phase are those of a plasma instability in the inner magnetosphere and do not require reconnection to have been initiated first. Given that reconnection is considered to be a key component of global substorm activity, this leaves an apparent disconnect between the initiation of the instability and the reconfiguration of the magnetic field.This project aims to improve our understanding of the substorm processes within the magnetosphere, placing observations of the signatures of reconnection, magnetotail reconfiguration and plasma instabilities in relative context: (i) comparing the relative timing of different in-situ and remotely detected substorm signatures including magnetospheric fast flows and ULF wave growth(ii) determining which observational features are common to all substorms and examining the implications of the presence or lack thereof of non-common features (iii) examining the occurrence and impact of 'substorm signatures' during periods of substorm and non-substorm activity.This project will involve the examination of a variety of data sources including in-situ observations from missions such as Cluster, THEMIS and MMS as well as ground-based data from magnetometer chains and auroral all-sky cameras.