A study of the characteristics of the polar rain has been completed using data from the SSJ/3 sensor on the Defense Meteorological Satellite Program F2 satellite. Approximately 262 polar passes of data were analyzed. Orbits were chosen which exhibited an extended region of polar rain and for which solar wind and interplanetary magnetic field (IMF) data were available. For each pass, 45-s-averaged spectra of polar rain were calculated. In approximately 70% of the cases the resulting spectra are well fit by a single simple Maxwellian distribution with an average temperature of 80¿13 eV and an average density of 5.5¿10-2¿3.8¿10-2 cm-3. In the remaining 30% of the cases an additional hot component was fit by a second Maxwellian.

The distribution of temperatures for the hot component shows a prominent peak at ~525 eV but extends over a range from 300 to 2800 eV. The high-energy component has an average density of 6.0¿10-4¿3.5¿10-4 cm-3. The distribution of the ratios of the high-energy to low-energy temperatures has a prominent peak between 5 and 8. No clear relationship was found between the temperatures of the solar wind and the polar rain or their number densities. The occurrence of the events studied is strongly dependent on the Bz component of the IMF being negative. The intensity of the polar rain is dependent on both the orientation and the magnitude of the IMF Bx and By components. For By positive (negative) in the north (south) pole the intensity of the solar rain increases exponentially with the magnitude of By. For By negative (positive) in the north (south) pole the level of the polar rain is constant as a function of By.

Essentially the same behavior is seen if comparable separations are made using the IMF Bx component. Differentiation of whether the behavior is primarily dependent on Bx or on By was not possible. Positive gradients in the intensity of the polar rain were found primarily along the satellite trajectory in the dusk to dawn direction. For By negative (positive) in the north (south) pole these gradients are most priminent. For the opposite case of By negative (positive) in the north (south) pole the gradient remains dusk to dawn, or the polar rain level is flat. Only in a small number of cases in either cap does the gradient reverse and appear in the dawn to dusk direction.