Global Plasmaspheric Electron Density Simulations of Pre-dawn and Post-dusk Geomagnetic Events Observed by the Van Allen Probes

Abstract:

We use in situ measurements by the Van Allen Probes (RBSP) to validate a globally applicable plasmaspheric electron density model (RAM-CPL), which is based on ionospheric outflow rates and electric field drivers as proxies for system refilling and erosion respectively. The model is a key component of the RAM-CPL suite in describing the temporal evolution of plasma density in the equatorial plane of the magnetosphere. In addition to considering absolute density values, this study employs a composite definition of the plasmapause boundary as a standard metric for comparison between observations and the model. Because the dynamics of the plasmasphere are governed on different timescales ranging from minutes to days, we consider geomagnetic events for which the RBSP satellites are at conjunction to sample fine-scale density variation as well as large-scale structure. Furthermore, the pre-dawn and post-dusk sectors of the observations provide adequate constraints on the candidate electric field drivers of the plasmasphere. The good agreement attained by the RAM-CPL plasmasphere model can be utilized to predict density conditions in magnetic local time and L-parameter sectors distant from an RBSP orbit of interest. These simulations reproduce plasmapause radial locations to within 0.6 Earth radii (RE) of RBSP observations and we investigate the competing effects of plasmaspheric refilling and erosion on model performance.