Electron density profile in the magnetosphere deduced from in situ electron density and wave normal directions of omega signals observed by the Akebono (EXOS D) satellite

Abstract

We describe a new method to construct the global plasma distribution in the plasmasphere using the electron density measured along the trajectory of the Akebono (EXOS D) satellite and the wave normal direction of Omega signals simultaneously observed by the same spacecraft. In this method the plasma density distribution is described by using the diffusive equilibrium model, with eight parameters, that is, die relative abundances and temperatures of ions, and the electron density at a reference altitude. This model is first fit in a least squares sense to the electron density observed along the spacecraft trajectory. The fit solution is not always unique. In such cases it is necessary to constrain the possible solutions further. Therefore we ray trace Omega signals from their source location and check if the wave normal directions at the spacecraft location are consistent with those observed. We present here three different examples of fitting methods in which fixed, freely fitted, and constrained fitted parameters yield reasonable plasma distributions.