Proton precipitation during magnetic storms in the plasmapause region according to the data from the Intercosmos-5 satellite

Abstract

The outer-zone >0.5 MeV proton behavior during magnetic disturbances is described according to measurements obtained from the low-altitude magnetically oriented satellite ‘Intercosmos-5’ for the period from December 1971 to April 1972. The satellite orbit allowed measurements to be made at invariant latitudes < 64°. During magnetic storms and Dst-depression events ( Dst≤30 γ) in the day 06–16 h LT sector the quasitrapped ( H min < 100 km) and enhanced trapped proton fluxes have been detected on L = 3–4.7. Both the precipitating (with pitch angle α≈0°) and quasitrapped protons have been found on the same L-shells in the evening and night (06–16 h LT) sectors. Analysis of the data has revealed that there are two zones of the storm-time proton appearance in the evening and night sectors. In the first zone, which is located at lower latitudes, most probably inside the plasmapause as projected to equatorial plane, only the quasitrapped protons appear. In the second zone, at higher latitudes, the proton fluxes were observed to be, as a rule, isotropic or with field-aligned anisotropy. The isotropic precipitation takes place, most probably, just outside the plasmapause. The coincidence between the position of the inner boundary of proton precipitation as measured by Intercosmos-5 and the plasmapause location as detected by Explorer-45 during the storm of 16 December 1971 is shown.