Precipitating and trapped ions and electrons observed at 840 km during the Great Magnetic Storm of February 1986

Abstract

A detailed picture is presented of the equatorward boundaries of the auroral ovals at dawn, morning, dusk, and evening for the three most disturbed days of February 1986. North–south symmetry for the boundaries of keV particles was good, and the differences between the ion and electron boundaries agreed with statistics which show the ion edge slightly equatorward of the electron edge at dusk, with the reverse for dawn. The electron boundary was most equatorward of the ion boundary for morning. Best symmetry and least difference were for evening, the sector nearest the central plasma sheet. Ions with energies from thermal to several hundred electron volts penetrated inward to L = 1.2. Initial penetration was confined mainly, if not exclusively, to the dawn sector. The sudden appearance of low‐energy ions deep in the plasmasphere at dusk and evening after storm maximum suggests corotation from a plasmapause as low as L = 1.7 at dawn. Low‐energy electrons rarely advanced equatorward of the keV electrons. On the other hand, keV electrons occasionally were detected about the equator, apparently in relation to the inward convection of the radiation belt. Very energetic, MeV, particles occurred near 52° MLAT, mainly after storm maximum and often unsymmetrically, which may reflect a characteristic akin to the South Atlantic Anomaly.