Space-Time Dynamics of the Earth’s Outer Radiation Belt and Wave Activity in May and December 2006

The paper examines the relationship between space-time variations in electron fluxes in the Earth’s outer radiation belt (OERB) and the wave activity — Pc5 pulsations (2–7 MHz) observed during magnetic storms of different origin. Two magnetic storms of 2006 were considered: the storm of May 9–14 caused by the high-speed solar wind stream from a coronal hole that arrived to the Earth, and the storm of December 15–16 caused by a coronal mass ejection. The analysis of the OERB electron fluxes in a broad energy range (from 300 keV to >3.5 MeV) was based on measurements on board the Universitetsky-Tatiana satellite with a circular polar orbit. It was shown that the wave activity during the storm of December 15–16 was significantly higher than during the storm of May 9–14. During the main phase of the storm on December 15–16, the maximum wave activity shifted to lower latitudes compared to its pre-storm position. The outer Earth’s radiation belt also shifted after the December storm closer to the Earth – towards lower L. The maximum particle flux increased after the December storm by approximately an order of magnitude in the entire energy range. After the May storm, the maximum electron fluxes in the OERB decreased, and the position of the maximum changed little, shifting slightly toward high latitudes, which is also consistent with the spatial distribution of the wave activity of Pc5 pulsations at that time.