Observations of precipitating protons in the energy range 2.5 kev≤E≤200 kev

Measurements of precipitating protons in the energy range 2.5 - 200 keV have been made on Ov1-15 (1968-59A), a low-altitude polar satellite, with a combination of electrostatic analyzers and integral foil detectors. During disturbed times, precipitating proton fluxes in the range 10 million - 100 million/sq cm-sec are seen. On several occasions, it has been possible to compare the spatial distribution of precipitation with the plasmapause profile taken by Ogo 5 during all phases of magnetic storm activity. It is found that the near-earth boundary of maximum proton precipitation lies just inside the plasmapause. If observed pitch-angle distributions are classified according to whether the loss cone is nearly empty or otherwise, it is found that the corresponding 40 keV flux intensities and L values separate into two classes in a way described by weak vs strong pitch-angle diffusion. (Author)