CHANGES OF THE TOTAL ION PRESSURE IN THE NIGHTSIDE INNER MAGNETOSPHERE

The total ion pressure has been considered in the range of the magnetic shell parameter L from 2.3 to 6.7 in the nightside magnetosphere. The data of the LEPA (0.1-30 keV ions and electrons) and EPAS (21.5- 285 keV electrons and 37-3200 keV ions) particle detectors and the magnetic field measurements onboard CRRES satellite have been used. The dynamics of the whole energy range of the electrons and ions have been considered to estimate the total plasma pressure during several events in disturbed periods before the substorm onsets. We consider here two events in more details. As the estimated electron contribution in the total pressure is small, we analyze the total ion pressure supposing that all ions are the protons. Besides, we consider also the pressure of the low-energy ions (LEPA) and high- energy ions (EPAS) separately. The estimated total ion pressure reaches a maximum at L ~ 3 and then a gradual decrease with increasing L. We found that an additional peak in the radial profile of the total ion pressure appears at L ~ 4.6 - 4.9. This peak coincides with an enhancement of LEPA portion of the ion pressure which disturbs the nearly monotonous drop of energetic ion pressure as a function of the parameter L. The penetration of the plasma sheet ions into the inner magnetosphere is discussed and compared with other observations.