RELATIONSHIP BETWEEN THE OBSERVED AND MODELED MODULATION OF THE DAYSIDE IONOSPHERIC CONVECTION BY THE IMF B-Y COMPONENT

The Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Prop agation (IZMIRAN) electrodynamic model (IZMEM) provides global pattern s of polar ionospheric potential and is parameterized by the interplan etary magnetic field (IMF). Given IMF conditions measured by an upstre am satellite, the model yields a good global approximation to the pola r ionospheric convection patterns assuming the proper time delay. Whil e the model assumes static patterns and is based upon statistical regr ession analysis of high-latitude magnetometer data, it can furnish an appropriate global context within which to examine time-varying phenom ena. We use the IZMEM model to further develop our understanding of th e coordinated analysis of Greenland radar, riometer, and magnetometer data on August 2, 1991, which is one of the geospace environment model ing program intervals. The event is characterized by geomagnetic pulsa tions observed near local magnetic noon, having a 25-min period and po leward phase propagation. A modulation of the intensity and orientatio n of the convection electric field is observed by the Sondrestrom inco herent scatter radar. Modeled global convection patterns show striking agreement with observations in the ar ea covered by the radar field o f view. We interpret observed phenomena as a direct ground-based evide nce of the IMF B-y component reconnection at the dayside magnetopause.