AVERAGE TERRESTRIAL RING CURRENT DERIVED FROM AMPTE CCE-CHEM MEASUREMENTS/

The present study attempts to analyze the average ring current density and pressure in the magnetospheric equatorial plane (as a function of geocentric distance and local time) based on the AMPTE/CCE-CHEM proto n distributions according to two different AE ranges, corresponding to a low (AE<100 nT) and a moderate (100 nT<AE<600 nT) geomagnetic or au roral activity. In order to obtain a statistically significant databas e for a high spatial resolution, the data were averaged over 2 years. The results provide a trend of the ring current and show its general a verage features as a function of geomagnetic activity. In particular, the total ring current is dominated by the pressure gradient term, res ulting in an eastward current in the inner magnetosphere (L<4.5) and a n extended westward current at higher altitudes. The westward current is always stronger than the eastward current. Moreover, the ring curre nt system is a function of magnetic local time, exhibiting a noon-midn ight asymmetry in general, as well as a function of geomagnetic activi ty exhibiting an enhancement of about 20% during active times (in midn ight-dusk region only). The location of the total current peak in the midnight sector is at about MLT=23 00, and its changes with magnetic a ctivity are interpreted as an effect of the particles injection from t he tail during the storms/substorms. The derived current values are co mpared to previous model predictions and observations.