The Hemispheric Difference in Electric Potential and Electron Precipitation Observed by DMSP in the Auroral Zone

In this case study, we focus on how hemispheric differences in the electric potential distribution in the auroral zones are related to hemispheric differences in the energetic particle precipitation that indicate the presence of field-aligned potential drops. Utilizing data during the spring and fall equinox in 2013 and 2014 from the Defense Meteorological Satellite Program (DMSP) F16 and F17 satellites, we systematically examine simultaneous measurements of plasma drift velocity and particle precipitation in magnetically conjugate regions across the auroral zone in both hemispheres. This allows us to establish the degree to which the interhemispheric differences in ionospheric electric potential may be accounted for by field-aligned potential drops. Thirty-seven eligible cases examined show accelerated electron energy spectra at conjugate locations in the northern and/or southern hemispheres. Of these 37 cases, 23 show conjugate differences in electric potential that agree qualitatively with the observed electron acceleration and average energy of precipitating electrons in each hemisphere. This result suggests that the hemispheric differences in ionospheric electric potential in the auroral zone may be most frequently accounted for by field-aligned potential drops along the magnetic flux tubes connecting conjugate points to the equatorial plane. The spatial and temporal variability of the potential distribution, electron precipitation, and magnetic field configuration could account for deviations from the normally observed situation in the remaining cases. More magnetically conjugate observations at various altitudes in both hemispheres are needed to investigate this hemispheric coupling in more detail. 5 conjugate observations, having accelerated electrons in one hemisphere, show agreement in differences in potential and electron energy18 conjugate observations, having accelerated electrons in both hemispheres, show agreement in differences in potential and electron energyPotential drops along magnetic flux tubes connecting to the equatorial plane could account for the observed potential differences