RELATIVE CONCENTRATION OF HE-1 RETARDING ION MASS-SPECTROMETER( IN THE INNER MAGNETOSPHERE AS OBSERVED BY THE DE)

With observations from the retarding ion mass spectrometer on the Dyna mics Explorer 1 from 1981 through 1984, we examine the He+ to H+ densi ty ratios as a function of altitude, latitude, season, local time, geo magnetic and solar activity. We find that the ratios are primarily a f unction of geocentric distance and the solar EUV input. The ratio of t he densities, when plotted as a function of geocentric distance, decre ase by an order of magnitude from 1 to 4.5 R(E). After the He+ to H+ d ensity ratios are adjusted for the dependence on radial distance, they decrease nonlinearly by a factor of 5 as the solar EUV proxy varies f rom about 250 to about 70. When the mean variations with both these pa rameters are removed, the ratios appear to have no dependence on geoma gnetic activity, and weak dependence on local time or season, geomagne tic latitude, and L shell.