Ionospheric signatures of magnetospheric convection

Abstract

Convection plays a major role in determining the characteristics of the high‐latitude ionosphere and the processes that drive magnetospheric convection are reflected in the ionospheric configuration. Average patterns of ionospheric convection observed with the Chatanika incoherent scatter radar, when mapped along magnetic field lines to the equatorial plane, delineate regions of earthward convection within the magnetotail that either proceed sunward to the dayside magnetopause where reconnection with the IMF may occur or that join the antisunward circulation along the magnetospheric flanks at dusk and dawn. Summer and winter patterns of ionospheric convection and F region density are examined in terms of the corresponding patterns of magnetospheric circulation. It is found that ionospheric ionization troughs at dusk and dawn are associated with sunward convection of low‐density plasma from the night sector and that plasma in the vicinity of the dawn and dusk electric field reversals circulates at high latitudes away from the solar ionization source at noon. Convection into the cleft from low latitudes populates the polar cap with high density solar‐produced plasma. Winter densities in this region were three times those seen in summer. Plasma exiting the polar cap is convected away from midnight in the equatorward portion of the regions of sunward convection at auroral latitudes. Characteristic features of the polar cap plasma serve to identify plasma following such convection trajectories.