Solar-induced variation of proton precipitation near the equator

This paper reports the solar condition dependences of the quasi-trapped component (low energy) of the proton population of energy 0.65–35 MeV which peaks in the equatorial zone centered on the minimum magnetic field equator in the altitude range 170–850 km. The proton populations compared pertain to AZUR observation in 1969–1970, S81-1 mission observation in 1982 and EXOS-C observation during 1984–1986. In the equatorial zone, the dependence of the flux normalization constant, which represents the absolute proton population, upon factors like L (1.1–1.3), B (0.29–0.32 gauss), latitude ( ± 20°), longitude (0–360°) and anisotropy index q (~6–12) of the pitch angle distribution function is not so significant in the given range of these factors as it is upon the solar epoch. It is found that the absolute proton flux in 1982 was, at least, forty times that in 1984–1986 and, almost, three times that in 1969–1970, possibly, due to, varying solar conditions in those epochs.