GEM: Evolution of Plasmasphere, Plumes and Fine Structure

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project will assemble a database of number density measurements in the plasmasphere from 5 different satellite missions (OGO-5, ISEE-1, CRRES, Polar, and IMAGE). The missions had complementary orbits and spanned roughly 4 solar cycles. The cycle of erosion and recovery of the plasmasphere depends on the relative changes of the strength of magnetospheric as well as on the time since the last major change in convection. Therefore, this project will employ a superposed epoch time analysis. Convection events ranging from mild to severely disturbed will be identified using an automated algorithm and epoch times will be assigned to all data. The project will create a global empirical model of plasmaspheric density that includes both plumes and fine-scale structure, parameterized by space, selected geomagnetic indices, epoch time, sunspot number, and season. Fine structure analysis will be done by isolating from the global-scale distribution those density features whose size falls below a pre-defined length scale. The fine structure will then be characterized by its dependences on the various parameters being used in the model. Comparisons of the model results with number densities obtained from LANL and DMSP spacecraft (two missions not used in the models creation) will be used to validate the model. This model will be used along with specific case studies from the 5-mission database to examine the time-dependent morphology of plasmaspheric plumes, the details of dayside transport of the eroded plasma, and the fine-scale structures that are created during the transport. Plasmaspheric plumes can slow down the dayside reconnection rate (modulating the energy input to the entire magnetosphere). In addition, the global density distribution, and the fine structure that prevails throughout the plasmasphere exert a significant influence upon the growth, propagation, and effectiveness of waves that scatter energetic particles. All results will be published and posted to the GEM Wiki website, and to a mirror site hosted by Southwest Research Institute.