Polar/Toroidal Imaging Mass-Angle Spectrograph observations of suprathermal ion outflow during solar minimum conditions

We present observations of the magnitude and variability of escaping suprathermal ions in the energy per charge range of 15 eV/e to 33 keV/e. The data were obtained from the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) on the Polar spacecraft from April 1996 to September 1998 over the Earth's southern Polar cap during solar minimum conditions. The net outflow rates of ionospheric ions derived from this data set are significantly different from those inferred from analysis of similar data obtained at higher altitudes from the Dynamics Explorer (DE) 1 satellite. The data present a clear picture of the seasonal variation of ion outflow as a function of solar illumination (i.e., season). We conclude that the differences between the present results and previous DE 1 estimates of the magnitude of escaping suprathermal ions can be explained by energization of the H+ component of the Polar wind above the 6000–8000 km altitude region, where the Polar data were acquired. We also note that seasonal variations in He+ outflow presented here are not as large as those reported previously.

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