ELECTRIC-FIELD IN THE EQUATORIAL IONOSPHERE

A model of the ionosphere as a global conductor is used to examine synchronous variations of electric fields and currents at high and low latitudes. The special form of a boundary value problem and a multigrid numerical method permit investigation of auroral field penetration to the equator. A model of field-aligned currents and conductivities for expansion and recovery phases of a substorm are suggested, which are in accordance with empirical models and with theory of field-aligned current dynamics. Electric field distributions near the equator, which were obtained as a result of calculations, are in accordance with observations during substorms. It is shown that the contribution of high latitude sources to low latitude electric fields and currents during quiet-time periods is comparable with that given by dynamo fields. The nature of the post-sunset peak of the zonal electric field at the equator and seasonal variations of this peak are explained.