Horizontal transmission of the polar electric field to the equator

Abstract

A mode which makes possible the instantaneous transmission of the polar ionospheric electric field to the equator is obtained. The problem is solved analytically as an initial-boundary value problem by assuming a plane Earth-ionosphere waveguide system composed of the metallic ionosphere with vertical static magnetic field and the perfectly conducting Earth, The TM 0 (zeroth-order transverse magnetic) waveguide mode excited by the polar electric field propagates instantaneously to the low-latitude accompanying the electric field with the same direction as the polar field. The simultaneous occurrence of the PRI (preliminary reverse impulse) of the SC∗ and the DP-2 geomagnetic variations in the high-latitude and equatorial regions are interpreted in terms of the polar originated electric field associated with the TM 0 mode. The geometrical attenuation of the transmitted electric field due to the finite scale of the polar field causes the disappearance of the PRI at low-latitudes, but the PRI appears again in the dayside equatorial region because of the enhanced ionospheric conductivity. The twin current vortices for the high-latitude PRI are interpreted as the Hall current caused by the polar electric field with finite scale. It is suggested that the direct current flows between the magnetosphere and the equatorial ionosphere via the polar ionosphere, when a large scale electric field is generated in the magnetosphere. From the mid-latitude ionospheric part of this current, the electric field may be mapped upward along the magnetic lines of force into the low L-value hydromagnetic region and as a result the penetration of the magnetospheric electric field into the plasmasphere is achieved by way of the Earth-ionosphere waveguide.