Cross-polar cap horizontalEregion currents related to magnetic disturbances and to measured electric fields

Abstract

Ground-based polar cap magnetometers and rocket-borne magnetic and electric field observations in the polar cap ionosphere seem to support the existence of a horizontal cross-polar cap ionospheric E region Hall current, whereas a survey of polar cap Ba release experiments leads to the conclusion that the ground-based magnetic disturbances cannot be explained by an overhead Hall or Pedersen current. An attempt to resolve the apparent paradox is made by considering the orders-of-magnitude difference in dayside and nightside E region plasma density. This leads to a proposed existence of field-aligned currents in the polar cap and to an estimate of the magnetic disturbance from polar cap and auroral oval field-aligned currents.