Effects of Solar Wind Plasma Flow and Interplanetary Magnetic Field on the Spatial Structure of Earth's Radiation Belts

Based on the statistical data measured by Van Allen Probes from 2012 to 2016, we analyzed the effects of solar wind plasma flow and interplanetary magnetic field (IMF) on the spatial distribution of Earth's radiation belt electrons (>100 keV). The statistical results indicate that the increases in solar wind plasma density and flow speed can exert different effects on the spatial structure of the radiation belts. The high solar wind plasma density (>6 cm(-3))/flow pressure (>2.5 nPa) and a large southward IMF (B-z < 6 nT) usually appear in the front of high-speed solar wind streams (> 450 km/s), and they tend to narrow the outer radiation belt but broaden the slot region. In contrast, the increase in solar wind flow speed can broaden the outer radiation belt but narrows the slot region. When the solar wind speed exceeds 500 km/s, the outer radiation belt electrons can penetrate into the slot region (L < 3) and even enter the inner radiation belt (L < 2). The lower-energy electrons penetrate into the deeper (smaller-L) region than the higher-energy electrons.