The Effects of Geomagnetic Activities on Acceleration Regions of Radiation Belt Electrons

Abstract

Solar wind and magnetospheric processes play important roles in relativistic electron acceleration in the Earth's outer radiation belt. However, how geomagnetic activity affects the acceleration region of relativistic electrons is still not clear. Here we first report the local acceleration regions during the strong storm of 1 June 2013. The first local acceleration region occurs at the lower L shell (L* ∼ 4.0) during the early recovery phase, which is associated with non‐continuous substorm activities. The second local acceleration region occurs at the higher L shell (L* ∼ 5.0) during the late recovery phase, which is associated with continuous substorm activities. To provide a more comprehensive picture, we additionally analyze two storm events with different geomagnetic activities. These events suggest that (a) the strong storm makes it possible for the local acceleration regions to occur at different L shells; (b) the timing, intensity, and duration of substorms during the recovery phase are crucial to the location and dynamics of the local acceleration region. These results can help us further understand the dynamics of relativistic electrons in the Earth's outer radiation belt.

A Statistical Study on the Acceleration Conditions of Ultrarelativistic Electrons in the Earth's Outer Radiation Belt During Geomagnetic Storms

“…This is consistent with the results of Tang et al. (2023b). These intense and continuous substorms during the recovery stage are more likely to lead to the acceleration of ultrarelativistic electrons with high energies (Figure 7).…”

“…For the storm events that substorms occurred during the early recovery stage, the L* shells of the peak fluxes of ultrarelativistic electrons (L* max2 , L* max3 , L* max4 , and L* max5 ) (the local acceleration region) are smaller (the blue triangle symbols in Figure 8). This is consistent with the results of Tang et al (2023b). These intense and continuous substorms during the recovery stage are more likely to lead to the acceleration of ultrarelativistic electrons with high energies (Figure 7).…”

“…As seen from Figure 8, the L* shells of the peak fluxes of relativistic and ultrarelativistic electrons are usually smaller for the storm events with substorms mainly occurring during the early recovery stage (the blue triangle symbols), while the L* shells of the peak fluxes of relativistic and ultrarelativistic electrons are usually higher for the storm events with substorms occurring during both the early and later recovery stages (the red triangle symbols). This is also consistent that the timing, intensity, and duration of substorms during the storm recovery phase are important to the location and dynamics of the local acceleration region (Tang et al, 2023b). From Figure 8, L* max1 has a good correlation with L* max2 , L* max3 , L* max4 , and L* max5 (cc = 0.89, 0.89, 0.97, and 0.93), and enhancements of ultrarelativistic electron fluxes mainly occurred near the heart of the outer radiation belt.…”

“…Tang et al. (2023b) also showed that the timing, intensity, and duration of substorms during the storm recovery phase were crucial to the location and dynamics of the local acceleration region.…”

“…Many previous studies have focused on the effect of the solar wind (e.g., Iles et al., 2002; Miyoshi et al., 2013; Reeves et al., 2011; Turner et al., 2019; Wing et al., 2016; Zhao et al., 2017) and magnetospheric processes (e.g., Drozdov et al., 2019; Forsyth et al., 2016; Gu et al., 2020; Jaynes et al., 2015; Kim et al., 2015; L. Y. Li et al., 2009; Reeves, 1998; Reeves et al., 2003; Schiller et al., 2014; Su et al., 2014; Tang et al., 2016, 2017b, 2023a, 2023b; Turner et al., 2015) on relativistic electrons in the Earth's outer radiation belt. However, the statistical analysis of the influence of solar wind and magnetospheric processes on ultrarelativistic electrons in the outer radiation belt was relatively few before the launch of the Van Allen Probes.…”