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，它包括夜侧极光的快速增强，地面上的磁扰动，环电流和辐射带的增强以及磁层中更远的等离子体的加热。亚暴在约30分钟内释放约1 PJ （1015 J）的能量，其中大约一半的能量被倾倒到大气中。这种能量释放及其相关过程有可能对空间和地面上的技术造成危害，使亚暴成为空间天气的一个关键组成部分。在标准的亚暴模型中，亚暴有三个阶段：一个大约1小时的生长阶段，在此期间，磁层和太阳风之间的重新连接为地球的磁尾增加了能量；持续约20分钟的膨胀阶段，其中一些能量迅速释放，产生明亮的极光并重新配置地球磁场；还有一个持续1-2小时的恢复阶段，在此期间，能量继续释放，但速度越来越慢，系统开始恢复到亚暴前的状态。地球磁尾磁场的重联重构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。它们也被推断为启动亚暴活动的关键部分（所谓的亚暴启动的“由外而内”模式）。然而，最近的研究表明，亚暴膨胀阶段的初始特征是内磁层中等离子体不稳定的特征，并且不需要首先重新连接。考虑到重联被认为是全球亚暴活动的关键组成部分，这在不稳定的开始和磁场的重新配置之间留下了明显的脱节。该项目旨在提高我们对磁层内亚暴过程的理解，在相对背景下观察重联、磁尾重构和等离子体不稳定性的特征。(i)比较不同的原位和远程探测到的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）确定所有亚暴共有的观测特征，并研究存在或缺乏非共同特征的影响；（iii）研究亚暴和非亚暴活动期间“亚暴特征”的发生和影响。该项目将涉及对各种数据源的检查，包括来自Cluster、THEMIS和MMS等任务的现场观测，以及来自磁强计链和极光全天相机的地面数据。

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.