Outflowing ionospheric oxygenion motion in a reco

Authors: Wodnicka E B Banaszkiewicz M

Publish Date: 1997/01/31

Volume: 15, Issue: 1, Pages: 5-16

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Abstract

Abstract During substorms largescale changes of the topology of the Earths magnetosphere following the variation of the characteristics of the interplanetary medium are accompanied by the induction of the electric field In this study a model of a timedependent magnetosphere is constructed and the largescale features of the induced electric field are described Localtime sectors with upward or downward fieldaligned component and with intense perpendicular component of the electric field are distinguished The electricfield structure implies the existence of outflow regions particularly effective in ion energization With the vector potential adopted in the study the region from which the most energized ions originate is defined by the localtime sector near 2100 MLT and latitude zone near 71° MLAT The motion of ionospheric oxygen ions of energy 03–3 keV is investigated during a 5min reconfiguration event when the taillike magnetospheric field relaxes to the dipolelike field As the characteristics of plasma in the regions near the equatorial plane affect the substorm evolution the energy pitch angle and the magnetic moment of ions in these regions are analyzed These quantities depend on the initial energy and pitch angle of the ion and on the magnetic and electric field it encounters on its way With the vector potential adopted the energy attained in the equatorial regions can reach hundreds of keV Three regimes of magneticmoment changes are identified adiabatic oscillating and monotonous depending on the ion initial energy and pitch angle and on the magnetic and electricfield spatial and temporal scales The implications for the global substorm dynamics are discussed

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