Simulateneous spectral variation of energetic ions in the nightside magnetosphere and upstream from the bow shock

Abstract

We performed an analysis of multispacecraft energetic particle and magnetic field observations from the PROGNOZ-10, CCE/AMPTE and IMP-8 spacecraft in order to investigate whether inverse energy dispersion in the upstream region can be produced by leakage of magnetospheric ions, and then to determine whether acceleration or propagation processes are responsible for this phenomenon. In this brief report we present observations obtained between 1700 – 2300 UT, on day 235, 1985 which show that, during times of substorm injection events, inverse energy dispersion (flux increase and hardening of the spectrum) of energetic (∼10–∼300 keV) ions were observed in the nightside magnetosphere (CCE/AMPTE) and in the region upstream from the bow shock (PROGNOZ-10) simultaneously (within min. Most of the observations are not consistent with the predictions of a Fermi types acceleration at the now shock, whereas they are in general consistent with a magnetospheric source of upstream ions; however, the absence of significant delay time between upstream and magnetospheric ion variations is not consistent with normal drifting times of energetic ions in the nightside magnetosphere. We suggest that the simultaneous detection of spectral hardening in the upstream region and the nightside magnetosphere was probably due to a global reconfiguration of the magnetospheric field, which produced electric fields and accelerated ions over extended regions of the Earth's magnetosphere.