Modeling Radiation Belt Electron Dropouts During Moderate Geomagnetic Storms Using Radial Diffusion Coefficients Estimated With Global MHD Simulations

Abstract

The Earth's outer radiation belt hosts geomagnetically trapped relativistic and ultra-relativistic electrons of highly dynamic fluxes located mainly at L = 3-7. These populations of penetrating particles are hazardous to spacecraft electronic systems in space (e.g., Baker et al., 2018). It is well established that flux variability in the outer belt arises from the significant loss and acceleration of these electrons usually associated with active geomagnetic conditions. These dynamic mechanisms may lead to the occurrence of a flux dropout or flux enhancement, or even no flux changes in case of a balance between loss and acceleration processes (Reeves et al., 2003).The sudden depletion or even extinction of radiation belts affecting several energy levels and L shells defines a flux dropout (

Rapid Acceleration Bursts in the Van Allen Radiation Belt

“…Similarly, during a recovery phase of a storm, the newly trapped electrons can be transported inwards and thus accelerated by the ULF waves (e.g., Ozeke et al., 2020; Silva et al., 2022) or accelerated locally due to the interaction with hiss (e.g., J. Li et al., 2019) or chorus waves (e.g., Horne et al., 2005; Hua et al., 2022). Lower energy electrons (1–10s keV) are also often impacted by the presence of kinetic Alfven waves in the auroral regions of the magnetosphere (see, e.g., review by Lysak (2023), and references within).…”

“…Similarly, during a recovery phase of a storm, the newly trapped electrons can be transported inwards and thus accelerated by the ULF waves (e.g., Ozeke et al, 2020;Silva et al, 2022) or accelerated locally due to the interaction with hiss (e.g., J. Li et al, 2019) or chorus waves (e.g., Horne et al, 2005;Hua et al, 2022).…”

Determination of Outer Radiation Belt MeV Electron Energization Rates and Delayed Response Times to Solar Wind Driving During Geomagnetic Storms

“…The likely causes of magnetic depressions stated by (Balikhin, Sibeck, et al, 2012) are that electrons inside and outside the dips are separated and the high energy electrons supply to maintaining the pressure balance inside these depressions. Silva et al (2022) stated that there are multiple reasons for flux dropouts occurrences. The common reason, as mentioned in the previous paragraph is variations of flux in the outer radiation belt that transpires from notable acceleration and loss of electrons, which are generally associated with active geomagnetic conditions.…”

“…In the case of CME-driven storms, the impact of sheath and ejecta on radiation belts is quite different (Pokhotelov et al, 2016). This dropout is possibly accompanied by MeV electron flux recovery which is a consequence of local acceleration substituting on seed populations which is caused by whistler-mode chorus wave interactions throughout substorms and inward radial diffusion Green and Kivelson (2004), Jaynes et al (2015), Summers et al (1998), Silva et al (2022). In the slot region, there is a flood of new electrons in tens to a few hundred keV electrons during the main phase.…”

“…The multi-MeV electron systems wave-induced precipitation are probably magnified during storms and the consequence of this gives fast localized electron dropouts ascribed to electromagnetic ion cyclotron (EMIC) wave interactions. Silva et al (2022), Shprits et al (2017), Summers et al (1998).…”