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

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

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.