Abstract
Microbursts, short-lived but intense electron precipitation observed by low-Earth-orbiting satellites, may contribute significantly to the losses of energetic electrons in the outer radiation belt. Their origin is likely due to whistler mode chorus waves, as evidenced by a strong overlap in spatial correlation of the two. Despite previous efforts on modeling bursty electron precipitation induced by chorus waves, most, if not all, rely on the assumption that chorus waves are ducted along the field line with zero wave normal angle. Such ducting is limited to cases when fine-scale plasma density irregularities are present. In contrast, chorus waves propagate in a nonducted way in plasmas with smoothly varying density, allowing wave normals to gradually refract away from the magnetic field line. In this study, the interaction of ducted and nonducted chorus waves with energetic electrons is investigated using test particle simulation. Substantial differences in electron transport are found between the two different scenarios, and resultant electron precipitation patterns are compared. Such a comparison is valuable for interpreting low Earth-orbiting satellite observations of electron flux variation in response to the interaction with magnetospheric chorus waves.
Highlights
Microbursts are impulsive precipitation of energetic electrons (∼30 keV to >1 MeV) from the magnetosphere into the atmosphere
The statistical analysis based on 11-years THEMIS wave measurement shows the transverse scale is mostly in the range of ∼250–800 km over 2 < L < 10 (Agapitov O. et al, 2018), which is consistent with Shen et al (2019) results from Van Allen Probes and THEMIS, where the averaged transverse size is ∼315 km over 5 < L < 6
We model electron flux response due to ducted and nonducted chorus elements and make comparison of the induced electron precipitation between the two cases
Summary
Microbursts are impulsive (typically lasting a few tenths of a second) precipitation of energetic electrons (∼30 keV to >1 MeV) from the magnetosphere into the atmosphere. The statistical analysis based on 11-years THEMIS wave measurement shows the transverse scale is mostly in the range of ∼250–800 km over 2 < L < 10 (Agapitov O. et al, 2018), which is consistent with Shen et al (2019) results from Van Allen Probes and THEMIS, where the averaged transverse size is ∼315 km over 5 < L < 6 These new observational features more thoroughly characterize the temporal and spatial scales of these individual elements, allowing for better modeling of the interaction of chorus waves with energetic electrons. In addition to temporal structures, spatial structures of microburst due to the nonducted chorus element will be revealed
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