Abstract

Plasma pressure distribution in the inner magnetosphere is one of the key parameters for understanding the main magnetospheric processes including geomagnetic storms and substorms. However, the pressure profiles obtained from in-situ particle measurements by the high-altitude satellites inside the plasma sheet and other regions of the magnetosphere do not allow tracking the pressure variations related to the storms and substorms, because a time interval needed to do this generally exceeds the characteristic times of them. On the contrary, fast movement of low-altitude satellites makes it possible to retrieve quasi-instantaneous radial or azimuthal profiles of plasma pressure along the satellite trajectory, using the precipitating particle flux data in the regions of isotropic plasma pressure. For this study, we used the low-altitude polar-orbiting Aureol-3 satellite data for plasma pressure estimation, and the IGRF, Tsyganenko 2001 and Tsyganenko 2004 storm time geomagnetic field models for the pressure mapping into the equatorial plane, and for the evaluation the corresponding volume of the magnetic flux tube. It was found that during quiet geomagnetic condition the radial pressure profiles obtained coincide with the profiles, obtained previously from the high-altitude measurements. On the contrary, the plasma pressure profiles change significantly during the development of storms and substorms. Nevertheless, three geomagnetic field models gave significantly different geomagnetic field profiles, those points out the necessity to develop a magnetically self-consistent model for description of the inner magnetosphere geomagnetic field. However, the common features observed for all models are: during geomagnetic storm the plasma pressure profiles became sharper; the position of the maximum of plasma pressure corresponds to expected one for given D st minimum; the maximum value of inner magnetosphere static pressure correlates with the solar wind dynamic pressure. Increase in the plasma pressure profiles indicates the possibility to consider the interchange instability as one of important factors for the development of the main phase of geomagnetic storm. © 2007 COSPAR.