A study of the statistical behavior of Ion temperatures from DE 1/RIMS

Retarding Ion Mass Spectrometer (RIMS) observations made from the Dynamics Explorer 1 satellite are averaged over one minute intervals and used to derive over 20,000 measurements of hydrogen ion temperatures. Temperatures are sorted by L-shell, local time, magnetic (Kp) and solar activity (F10.7). Average temperatures increase with L-shell. On lower L-shells, L < 3, the average temperatures increase with F10.7 but are generally less than 0.8 eV. No dependence on geomagnetic activity is found for L-shells less than 2. On higher L-shells, the average temperature increases with Kp, in some cases reaching a maximum of about 25 eV, but is usually less than 15 eV. In the lower L-shells, diurnal effects are small, less than 0.15 eV, for low F10.7 and less than 0.1 eV for high F10.7. On the higher L-shells the temperature appears to be independent of day-night conditions and of F10.7 flux. The behavior of the average temperature is indicative of both an ionospheric and an outer plasmaspheric heat source for plasmaspheric ions.