Technical Note: Ionospheric Boundaries Derived from Partial Auroral Images

Abstract. The high latitudes are a distinct region of the geospace environment, where strong coupling between the atmosphere, ionosphere, magnetosphere, and solar wind create distinct regions where different physical processes dominate. Because of this, modelling and statistical studies of the geospace environment at high latitudes should avoid mixing data measured in different regions (e.g., the polar cap, the auroral oval, and the sub-auroral regions). This study presents two new sets of poleward and equatorward Auroral Luminosity Boundaries (ALBs) along with functional definitions that relate these ALBs to the poleward and equatorward particle precipitation boundaries that mark the open–closed magnetic field line boundary (OCB) that demarcates the transition between the polar cap and auroral oval and the diffuse auroral boundary at the equatorward edge of the auroral oval. These data sets are obtained from space-based auroral imagers flown on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite and the Defense Meteorological Satellite Program (DMSP) constellation, that observe slices of the auroral oval in both hemispheres. The validation of the derived OCB locations against an independent polar cap proxy shows that the ALBs identified at the Lyman-Birge-Hopfield (LBH) Long wavelengths may be used together with other auroral boundary data sets in scientific studies.