Threedimensional current system in different phases of a substorm
Abstract
It is assumed that the threedimensional current system of a substorm passes three successive stages. (1) When a dawntodusk magnetospheric electric field appears, a current system with fieldaligned currents at the poleward boundary of the auroral zone arises. An equivalent ionospheric current system calculated, taking into account a daynight asymmetry of ionospheric conductivity, looks like the wellknown DP2 system including an eastward lowlatitude current and a greater magnitude of the dusk vortex in comparison with the dawn one. (2) An electric drift of plasma towards the Earth leads to the appearance of a westward partial ring current increasing in time. This current is closed by fieldaligned currents at the equatorward boundary of the auroral zone. The calculated equivalent current system is similar to the wellknown one of the precursory phase. (3) An increase of the auroral ionospheric conductivity during the expansive phase produces an increase of all currents and a turning of fieldaligned currents at the equatorward boundary of the auroral zone relative to those at the poleward one. The calculated equivalent current system is similar to the DP1 system.
 Publication:

Planetary and Space Science
 Pub Date:
 August 1974
 DOI:
 10.1016/00320633(74)900075
 Bibcode:
 1974P&SS...22.1231L
 Keywords:

 Earth Magnetosphere;
 Electric Fields;
 Magnetic Storms;
 Ring Currents;
 Auroral Zones;
 Field Aligned Currents;
 Interplanetary Magnetic Fields;
 Ionospheric Currents;
 Geophysics