MDS-1 Observations of Highly Energetic Electron Environment in the Inner Magnetosphere

Abstract

MDS-1 satellite observations demonstrated that highly energetic electrons in the outer radiation belt disappear during the main phase of the magnetic storm, and rebuilding of the highly energetic electrons is made during the recovery phase of the magnetic storm. A distribution of the new peak of highly energetic electron flux with respect to the distance from the Earth is inversely proportional to the magnitude of the magnetic storm. In case of the large storm, the outer electron belt is pushed toward the Earth, filling so-called slot region. It is of interest to identify that seed electrons are necessary around inner edge of the outer radiation zone to fill slot region. It was found that the location of the intense low frequency plasma waves, which appear during the storm recovery phase, coincides with the location of the peak intensity of the highly energetic electrons in the outer radiation belt. This coincidence strongly suggests that an internal acceleration process takes place which leads to a large increase in the intensity of highly energetic electrons in the outer radiation belt during the storm recovery phase. A seasonal variation of the outer radiation belt is identified. The increase in the intensity of the highly energetic electrons is large both in spring and autumn seasons. The magnetic activity is also large both in spring and autumn seasons. Correlation of the increase in the intensity of highly energetic electrons with the magnetic activity is identified. A solar cycle variation of the outer radiation belt is also identified. The location of the outer radiation belt was found closer to the Earth during the solar maximum periods and far from the Earth during the solar minimum periods. This variation is due to the evidence that large magnetic storms occur largely during the solar maximum periods, while small magnetic storms take place largely during the solar minimum periods, resulting in a long-term solar cycle variation with respect to the distance from the Earth.