Abstract :
The Akebono (EXOS-D) satellite made good observations of the radiation belt particles, covering an entire radiation belts in the evening sector during the space weather month (September 1999). During the campaign we had three magnetic storms; i.e. September 12–14, 22–23, and 27–28. On early September 23, the Dst index reached its minimum with −160 nT, showing a major magnetic storm, while both on September 13 and 27 the decrease of the Dst index was very gradual, having the minimum values of −70 nT and −65 nT, respectively. Even though the Dst variation was big during September 22–23, very little enhancement of MeV electrons was observed in the outer radiation belt during the storm recovery phase. On the contrary large enhancements in the intensity of MeV electrons took place for September 12–14 and 27–28, when the Dst variation were rather small. These large enhancements were made due to the prolonged magnetic activities during the storm recovery phase. The Russell-McPheron effect was evident; i.e. the 1IVIF was actually away for the cases of September 12–14 and 27–28. The increase in the intensity of MeV electrons was first seen in the heart of outer radiation belt and in lower energy. As time progressed the intensity of MeV electrons in far regions (L>5) increased, suggesting that both an internal acceleration of the electrons and an extremely large outward diffusion are taking place in the outer radiation belt.
