OUTFLOWING IONOSPHERIC OXYGEN-ION MOTION IN A RECONFIGURATING MAGNETOSPHERE

Citation
Eb. Wodnicka et M. Banaszkiewicz, OUTFLOWING IONOSPHERIC OXYGEN-ION MOTION IN A RECONFIGURATING MAGNETOSPHERE, Annales geophysicae, 15(1), 1997, pp. 5-16
Citations number
26
Categorie Soggetti
Astronomy & Astrophysics","Geosciences, Interdisciplinary","Metereology & Atmospheric Sciences
Journal title
ISSN journal
09927689
Volume
15
Issue
1
Year of publication
1997
Pages
5 - 16
Database
ISI
SICI code
0992-7689(1997)15:1<5:OIOMIA>2.0.ZU;2-8
Abstract
During substorms, large-scale changes of the topology of the Earth's m agnetosphere following the variation of the characteristics of the int erplanetary medium are accompanied by the induction of the electric fi eld. In this study a model of a time-dependent magnetosphere is constr ucted and the large-scale features of the induced electric field are d escribed. Local-time sectors with upward or downward field-aligned com ponent and with intense perpendicular component of the electric field are distinguished. The electric-field structure implies the existence of outflow regions particularly effective in ion energization. With th e vector potential adopted in the study, the region from which the mos t energized ions originate is defined by the local-time sector near 21 00 MLT and latitude zone near 71 degrees MLAT. The motion of ionospher ic oxygen ions of energy 0.3-3 keV is investigated during a 5-min reco nfiguration event when the tail-like magnetospheric field relaxes to t he dipole-like field. As the characteristics of plasma in the regions near the equatorial plane affect the substorm evolution, the energy, p itch angle, and the magnetic moment of ions in these regions are analy zed. These quantities depend on the initial energy and pitch angle of the ion and on the magnetic and electric field it encounters on its wa y. With the vector potential adopted, the energy attained in the equat orial regions can reach hundreds of keV. Three regimes of magnetic-mom ent changes are identified: adiabatic, oscillating, and monotonous, de pending on the ion initial energy and pitch angle and on the magnetic- and electric-field spatial and temporal scales. The implications for the global substorm dynamics are discussed.