Electron Phase Space Densities in Geostationary Orbits as Measured With GK2A, GOES-16, and GOES-17 Satellites

This study investigated electron phase space densities (PSDs) in geostationary orbits using data from Korea's geostationary satellite, GK2A, as well as GOES-16 and GOES-17 satellites. The PSDs were computed from electron fluxes measured by each satellite during a geomagnetically quiet period as defined by stringent conditions on geomagnetic activity. The conjunction of the satellites over invariant coordinates enabled electron PSDs from pairs of satellites to be compared to assess the extent of deviation of the PSD ratios from the expected ratio of one, as inferred from the Liouville theorem. The results show that PSDs from the satellites are sufficiently consistent to allow the estimation of the radial gradient of the PSDs. Comparisons of radial gradients estimated in this manner show that positive radial gradients prevail during geomagnetically quiet periods, whereas both positive and negative gradients may occur at similar frequencies during active periods. This study provides statistical insights into the physical mechanisms responsible for the observed radial gradient profiles based on findings from a wide range of local times during both geomagnetically quiet and active periods.