Asymmetric access and temporal variations of energetic solar protons at the polar caps

Abstract

Data from the low‐altitude polar orbiting satellite Ogo 6 showed that the ratio north/south (N/S) of the intensity of solar protons (Ep >50 Mev) over the earth's north (N) polar cap (λ >70°) to that over its south (S) polar cap (−λ >70°) was about 1.61±0.04 for the solar particle event of November 2, 1969, and 1.00±0.03 for the event of December 18, 1969, while the ratio N/S was 0.64±0.02 for the solar particle event of December 19, 1969. These results, considered together with the interplanetary magnetic field polarities and the interplanetary proton anisotropies, favor the open model of the magnetosphere. The data also showed a clear evidence of periodic temporal variations of the proton flux over the polar caps; the pulsation effects had frequencies in the same range as the Pc4 and Pc5 geomagnetic micropulsations and were attributed to magnetohydromagnetic waves.