Electron precipitation equatorward of the auroral oval and the mantle aurora in the midday sector

In the midday sector, the hard electron precipitation and the associated patchy aurora at geomagnetic latitude approximately 650 are the only auroral features (approximately 20 keV) located equatorward of the dayside auroral oval during intense and moderately disturbed geomagnetic conditions. The patchy luminosity in the midday and late morning sectors are identified as the active mantle aurora. The precipitating electrons reside mostly at energies greater than several keV with an energy flux of approximately > 0.1 erg cm-2 s-1 during geomagnetic active periods. This hard precipitation occurs in a region which is asymmetric in L.T. with respect to the noon meridian. The region extends from the morning sector to only early afternoon (13-14 M.L.T.) along the geomagnetic latitude circle of about 65-700. The model calculation indicates that the mantle aurora is produced by the precipitation of the energetic electrons which drift azimuthally from the plasma sheet at the midnight sector to the dayside magnetopause during magnetospheric substorms. (author)