Solar wind influence on the oxygen content of ion outflow in the high-altitude polar cap during solar minimum conditions

Abstract

We correlate solar wind and interplanetary magnetic field (IMF) properties with the properties of 0+ and H+ during early 1996 (solar minimum) at altitudes between 5.5 and 8.9 RE geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. Throughout the high-altitude polar cap we observe H+ to be more abundant than O+. O+ is found to be more abundant at lower latitudes when the solar wind speed is low (and Kp is low), while at higher solar wind speeds (and high Kp), O+ is observed across most of the polar cap. The O+ density and parallel flux are well organized by solar wind dynamic pressure, both increasing with solar wind dynamic pressure. Both the O+ density and parallel flux have positive correlations with both VswB IMF and Esw. No correlation is found between O+ density and IMF Bz, although a nonlinear relationship with IMF By is observed, possibly due to a strong linear correlation with the dynamic pressure. H+ is not as highly correlated with solar wind and IMF parameters, although H+ density and parallel flux are negatively correlated with IMF By and positively correlated with both VswBIMF and Esw. In this solar minimum data set, H+ is dominant, so that contributions of this plasma to the plasma sheet would have very low O+ to H+ ratios. Copyright 2001 by the American Geophysical Union.