Particle precipitation and ionospheric convection morphology in dayside aurora

Abstract

We present particle precipitation and ionospheric ion measurements from the Black Brant rocket IVB-38, which was launched from Cape Parry, Northwest Territories, Canada, on December 10, 1981, at 2314:58.5 UT as part of Project CENTAUR. The payload reached an apogee of 603 km and crossed two regions of electron precipitation. In both precipitation regions, the energetic-electron spectra were soft, with peak intensities of ≈1010 cm−2∙s−1∙keV−1 at 200 eV. The 100-eV electrons were anisotropic in the downcoming hemisphere (field aligned). The spectra varied with the electron pitch angle. They had larger characteristic energy at small pitch angles and revealed appreciable atmospheric degradation (and hence predicted optical auroral emissions) in the 300-km altitude region. No proton precipitation was observed. The topology of the ionospheric convection was found to be correlated with both the location and the drift motion of the aurora.