PROGRESSING IMF B-Y-RELATED POLAR IONOSPHERIC CONVECTION DISTURBANCES

A close correlation is frequently observed to exist between the dawn-d usk component of the interplanetary magnetic field (IMF B-y) and the e ast-west component of the ionospheric convective flow and associated H all currents (DPY currents) in the dayside polar cusp region. During i ntervals of southward interplanetary fields the IMF B-y-related convec tion disturbances may progress from the cusp region, where they are fi rst observed, across part of the dayside polar cap region. Examples of such progressing events as observed by an array of polar magnetometer s, by an imaging riometer, and by an incoherent scatter radar are pres ented. The relations between the geomagnetic perturbations, the ionosp heric absorption of radio waves, and the observed variations in the io n drift (convection) velocities, are discussed for the selected cases. These progressing disturbance events are considered to demonstrate th e merging of the interplanetary field with the geomagnetic field exten ding from the polar regions in an open magnetosphere like the model fi rst suggested by Dungey.