Inward shift of outer radiation belt electrons as a function of Dst index and the influence of the solar wind on electron injections into the slot region

摘要

The radial positioning of radiation belt electrons as a function of the Dst index and the controlling solar wind parameters for deep penetration of energetic electrons into the inner magnetosphere are investigated. Using 2-6 MeV electron data from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) from January 1995 to June 2004, we examine the L location of energetic electron deepest penetration, L location of the maximum flux, and L location of the maximum flux enhancement and variation over the duration of 119 moderate and strong isolated geomagnetic storms. We find that the L location of deepest penetration, L location of the maximum flux at the end of electron injections, and L location of the maximum flux variation have strong correlations with the minimum Dst index. Although the variation and radial positioning of radiation belt electrons is clearly associated with the Dst index, their deep penetration into the slot region (2 < L < 3) is not directly correlated with the Dst index in an obvious way. It is also known that the Dst index can be accurately predicted based on solar wind parameters. Thus, the necessary and sufficient combination of solar wind conditions for the occurrence of injection events into the slot region, between L = 2-3, are also investigated. We find a total of 23 injection events at L = 2.5 from 1995 to 2004 and that when certain solar wind conditions are met, an injection event at L = 2.5 is ensured. We also find that the electron flux preconditioning is an important factor influencing electron injections at L = 2.5. Key Points The L location of electron injection has strong correlation with Dst indexWe find sufficient solar wind condition for electron injection into slot regionElectron flux preconditioning is important for electron injections at L=2.5