HIGH-LATITUDE IONOSPHERIC ELECTRODYNAMICS AS DETERMINED BY THE ASSIMILATIVE MAPPING OF IONOSPHERIC ELECTRODYNAMICS PROCEDURE FOR THE CONJUNCTIVE SUNDIAL ATLAS-1 GEM PERIOD OF MARCH 28-29, 1992/

During the conjunctive SUNDIAL/ATLAS 1/GEM campaign period of March 28 -29, 1992, a set of comprehensive data has been collected both from sp ace and from ground. The assimilative mapping of ionospheric electrody namics (AMIE) procedure is used to derive the large-scale high-latitud e ionospheric conductivity, convection, arid other related quantities, by combining the various data sets. The period was characterized by s everal moderate substorm activities. Variations of different ionospher ic electrodynamic fields are examined for one substorm interval. The c ross-polar-cap potential drop, Joule heating, and field-aligned curren t are all enhanced during the expansion phase of substorms. The most d ramatic changes of these fields are found to be associated with the de velopment of the substorm electrojet in the post midnight region. Vari ations of global electrodynamic quantities for this 2-day period have revealed a good correlation with the auroral electrojet (AE) index. In this study we have calculated the AE index from ground magnetic pertu rbations observed by 63 stations located between 55 degrees and 76 deg rees magnetic latitudes north and south, which is larger than the stan dard AE index by about 28% on the average over these 2 days. Different energy dissipation channels have also been estimated. On the average over the 2 days, the total globally integrated Joule heating rate is a bout 102 GW and the total globally integrated amoral energy precipitat ion rate is about 52 GW. Using an empirical formula, the ring current energy injection rate is estimated to be 125 GW for a decay time of 3. 5 hours, and 85 GW for a decay time of 20 hours. We also find an energ y-coupling efficiency of 3% between the solar wind and the magnetosphe re for a southward interplanetary magnetic held (IMF) condition.