Space Plasma Seminar: Electron Density Distribution in the Earth's Plasmasphere: Models and Field-Aligned Measurements
Pavel Ozhogin, University of Massachusetts Lowell
Tuesday, April 9, 2013, 3:30pm
It is important to model the Earth's plasmasphere because of its profound role in space weather. The plasmasphere is a medium in which plasma waves propagate and interact with energetic particles. These waves can influence the radiation belts dynamics, which in turn can have significant impact on satellites and humans in space. A newly developed empirical model of the plasma density in the plasmasphere will be presented in this talk, along with several case studies of asymmetrical plasmasphere and two-dimensional density distributions. The developed empirical model is based on more than 700 density profiles along field lines derived from active sounding measurements made by the Radio Plasma Imager (RPI) onboard the IMAGE satellite. The resulting model depends not only on L-shell but also on magnetic latitude and can be applied to specify the electron densities in the plasmasphere between ~2000 km altitude and the plasmapause. The performance of the model is evaluated by comparison to four previously developed empirical plasmaspheric models and a theoretical diffusive equilibrium model. The performance is further tested against the in situ passive IMAGE RPI measurements of the upper hybrid resonance frequency. While the equatorial densities of different models are mostly within the statistical uncertainties, the clear latitudinal dependence of the RPI model presents an improvement over previous models. This electron density model combined with an assumed model of the ion composition can be used to estimate the time for an Alfven wave to propagate from one hemisphere to the other, to determine the plasma frequencies along a field line, and to calculate the ray paths for high frequency waves propagating in the plasmasphere.