GEM: The Dynamics of a Substorm: Auroral Streamers, Plasmasheet Flows, and Substorm Onset

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This project will investigate the hypothesized link between auroral streamers and events in the magnetotail leading to large auroral and geomagnetic disturbances called substorms. Substorms are powered by the explosive release of energy stored in the stretched magnetotail fields but the details of the energy release mechanism and associated dynamics have so far not been resolved. Understanding the cause of auroral substorms is a key problem in space weather research. Auroral streamers, the focus of this project, are finger-like structures in the auroral emissions aligned in the north-south direction on the nightside that travel from the poleward edge of the auroral oval towards lower latitudes. Observations for a number of events indicate that the auroral streamers are signature in the ionosphere of bursty flows of plasma far out in the magnetotail. The direction of their motion indicates that the bursty flows are transporting energy and plasma towards Earth from farther out in the magnetotail. A number of studies have observed auroral streamers reaching the initial location of substorms just prior to their explosive onsets leading to speculation that these flows may be involved in substorm triggering. If true, the characteristics and motion of auroral streamers will very likely give fresh insights into the long-debated dynamics of substorms. There are practical reasons for understanding how these large-scale auroral and geomagnetic disturbances are created. They lead to increased satellite drag, interfere with navigation and communications systems, and, in extreme cases, can disrupt electric power grids. This project has several unique aspects. In an effort to minimize or remove observer bias, automatic tracking routines will be applied to identify auroral streamers in all sky images during isolated substorms. A technique called Statistics of Point Processes will be used to determine if there is a relationship between auroral streamers and substorm onsets. In addition, correlation analysis will be performed to investigate the relationship between bursty flows in the magnetotail and auroral features. A further objective will be to investigate whether auroral beads are consistently present during substorm onsets. Auroral beads are structures thought to be produced by the ballooning instability in the magnetotail. A positive result would imply that the ballooning instability has a possible role in substorm onsets.