Characteristics of 2–6 MeV electrons in the slot region and inner radiation belt

Abstract

In this paper, the long‐term relativistic electron behavior in the often overlooked “slot” region and the inner belt was studied using the 2–6 MeV electron data from the SAMPEX satellite during 1992–2004. In particular, we investigated the penetration of the 2–6 MeV electrons to the slot region, their flux enhancement in the inner belt, and how these two processes are related to magnetospheric activity levels and solar wind parameters. It is found that the 2–6 MeV electron penetration (L < 3) usually takes place after those intense storms whose Dstmin is less than −130 nT. The penetration distance has a good correlation with the daily Dst minimum delayed by 3 days. However, it has little or no correlation with any of the individual daily solar wind parameters. A superposed epoch analysis shows a similar time lag between the peak values of the solar wind parameters/Dst index and the flux peak in the slot region at L = 2.5. Although the inner belt has fewer variations compared to the outer belt, it has its own response to different conditions. Analysis of the inner belt indicates that the flux enhancement is associated with high solar wind speed (>550 km s−1) as well as low solar wind density (∼4.4 cm−3). Either a couple of very extreme storms or recurrent intense storms will create conditions favorable for the MeV electron enhancement in the inner belt. However, without high‐speed solar wind on average, a series of intense storms alone are not sufficient to create inner belt electron flux enhancement.