The residual geomagnetic variation

The residual geomagnetic variations is investigated with emphasis on a regression analysis that takes account of the delayed effects of the solar wind. When the solar wind velocity is about 300 km/s, the equivalent current of the residual variation at high latitudes produces a two-vortex system with a current intensity of 100 kA (in summer); at midlatitudes the residual variation corresponds to the Sq system. It is suggested that the delayed effects are due to ionospheric dynamo action caused by collisions of neutrals with ions which undergo an ExB drift in the convection electric field.