GEM: A Statistical Study of the Substorm Sequence and Phenomena Associated with Expansion Onset

这个项目的重点是了解亚暴的本质，这是地球空间科学中的一个关键问题，迄今为止，它阻碍了开发空间天气干扰预测能力的努力。在极光电离层，亚暴被认为是极光突然变亮并向极地扩展。它是在地球上空磁层尾部伸展的爆炸能量释放的观测表现，最终将高纬度电离层的强电流分流，并产生高能带电粒子的沉淀。这些输入改变了那里的化学和电导率，并加热了耦合的电离层-上层大气。亚暴干扰会产生各种各样的环境影响，可能会增加卫星阻力，扰乱通信和导航系统，并在固体地球上产生能够破坏电网的电流。PI过去使用的一种标准技术是对亚暴的关键指标及其在时间和空间上的排序进行统计分析，并将其与各种亚暴动力学理论进行比较。最近新亚暴理论的发展为将新的和更新的数据集纳入扩展的统计研究提供了动力，该研究使用新开发的模式识别技术来消除观测特征识别中的偏差，并使用复杂的相关工具（例如，点过程统计）来建立物理过程的相对时间作为亚暴阶段的函数。本研究将全面列出有时间标记的亚暴特征（即极光带负湾、中纬度正湾、Pi2脉动、地球同步磁场双极化、极光公里辐射、磁尾流等），并在此基础上增加新的亚暴理论所暗示的特征集（即磁尾的暴体流、极向边界增强和极光区域的极光流光等）。观测信号列表中特征的相对时间将用于评估支持新的和以前的亚暴理论的证据。

This project is focused on understanding the nature of substorms, a critical problem in geospace science that so far has hindered efforts to develop a predictive capability for space weather disturbances. In the auroral ionosphere, a substorm is identified as a sudden brightening and poleward expansion of the aurora. It is the observational manifestation of an explosive energy release high above the Earth in the stretched tail of the magnetosphere that ultimately shunts strong currents through the high-latitude ionosphere and produces precipitation of high-energy charged particles. These inputs alter the chemistry and electrical conductivity there and heat the coupled ionosphere-upper atmosphere. Substorm disturbances produce a variety of environmental effects that can increase satellite drag, disrupt communications and navigation systems and induce currents in the solid Earth that are capable of damaging electric power grids. A standard technique that the PI has used in the past is to perform a statistical analysis of the key indicators of substorms and their sequencing in time and space and compare this against various theories about substorm dynamics. The recent development of a new substorm theory provides the motivation to incorporate both new and updated data sets into an expanded statistical study that uses newly-developed pattern recognition techniques to remove bias in the identification of observational signatures, and sophisticated correlation tools (for example, Statistics of Point Processes) to establish relative timing of physical processes as a function of substorm phases. This study will make comprehensive lists available of time-tagged substorm signatures (i.e., auroral zone negative bay, midlatitude positive bay, Pi2 pulsations, geosynchronous magnetic field dipolarization, auroral kilometric radiation, magnetotail flows, etc.) and add to these the set of signatures implied by the new substorm theory (i.e., bursty bulk flows in the magnetotail, poleward boundary intensifications and auroral streamers in the auroral region, etc.). The relative timing of features in the lists of observational signatures will be used to evaluate the evidence in support of the new and previous substorm theories.