Space Weather: Solar Wind/Magnetospheric Controls of Substorm Onset and Dynamics

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The primary objectives of this project are to investigate triggering mechanisms of substorm expansion phase onset and time scales of different substorm phases by using the technique of auroral oval positional analysis. The questions that will be addressed are: (1) Can reductions in convection trigger substorms (e.g. northward turning of the IMF)? (2) Can magnetospheric compression (e.g. Storm Sudden Commencements) trigger substorms? (3) What determines substorm times scales? (4) Can growth phase parameters predict substorm characteristics? These issues are of particular importance to the National Space Weather Program. The method to be used involves a massive statistical study. A large number (~ tens of millions) of global auroral images acquired from the ultraviolet imager (UVI) aboard the Polar satellite during the ISTP mission will address these questions. In addition to the images, solar wind plasma and magnetic field observations from the Geotail, Wind, and IMP-8 spacecraft, energetic particle data from the LANL series of geosynchronous satellites, magnetometer data from the GOES geosynchronous satellites and from the ground are compiled and analyzed to establish statistically meaningful results. This three-year effort includes substorm event identification and selection, auroral feature extraction (polar cap and oval location and auroral power), and correlation analysis. This project will investigate the temporal variations of the polar cap size, the oval boundary locations (both poleward and equatorward), and auroral power before and after auroral onsets to determine conditions that lead to the expansion phase onset. In addition, it will correlate interplanetary shocks with auroral onsets and provide a time-scale analysis of the different phases of substorms. All data products, including an onset list and substorm movies, as well as published results (journal reprints), will be made available to the general community through the web and CD-ROMs upon request.