Modeling the time‐evolving plasma in the inner magnetosphere: An empirical approach

Abstract

The global plasma distribution in the inner magnetosphere is directly related to the time‐evolving magnetospheric and solar wind conditions. However, it is difficult to derive a realistic global picture of the inner magnetosphere from in situ spacecraft measurements. In this study we approach this intriguing task by analyzing the H+ spectra from CRRES Magnetospheric Ion Composition Spectrometer (MICS) and Low‐Energy Magnetospheric Ion Composition Sensor (LOMICS) experiments (L shell between 3 and 9 and energies between 4 and 400 keV) during a large period including storm times as well as quiet times and by best fitting these proton spectra with those obtained via the empirical model proposed by Milillo et al. [2001]. The procedure is performed by tuning a subset of the model parameters in order to reconstruct the trend of the experimental data at the given location. It is shown that the profile versus time of the selected model parameters (strictly linked to the plasma distribution characteristics) is well correlated to the geomagnetic indexes. In particular, the storm‐time development of both the diffused population at high energies and the convected/injected particles in the range of tens of keVs are highlighted. Subsequently, the trend of the proton distributions on a global scale is reconstructed by means of the mentioned empirical model. Finally, the macroscopic features and their developments on a global scale are analyzed in terms of energy density, electric potential, and equatorial current density.