Rapid loss of the plasma sheet energetic electrons associated with the growth of whistler mode waves inside the bursty bulk flows

Abstract

[1] During the interval~07:45:36-07:54:24 UT on 24 August 2005, Cluster satellites (C1 and C3) observed an obvious loss of energetic electrons (~3.2-95 keV) associated with the growth of whistler mode waves inside some bursty bulk flows (BBFs) in the midtail plasma sheet (X GSM~À 17.25 R E ). However, the fluxes of the higher-energy electrons (≥128 keV) and energetic ions (10-160 keV) were relatively stable in the BBF-impacted regions. The energy-dependent electron loss inside the BBFs is mainly due to the energy-selective pitch angle scatterings by whistler mode waves within the time scales from several seconds to several minutes, and the electron scatterings in different pitch angle distributions are different in the wave growth regions. The plasma sheet energetic electrons have mainly a quasi-perpendicular pitch angle distribution (30°<α<150°) during the expansion-to-recovery development of a substorm (AE index decreases from 1677 nT to 1271 nT), and their loss can occur at almost all pitch angles in the wave growth regions inside the BBFs. Unlike the energetic electrons, the low-energy electrons (~0.073-2.1 keV) have initially a field-aligned pitch angle distribution (0°≤α ≤30°and 150°≤α ≤180°) in the absence of whistler mode waves, and their loss in field-aligned directions is accompanied by their increase in quasi-perpendicular directions in the wave growth regions, but the loss of the low-energy electrons inside the BBFs is not obvious in the presence of their large background fluxes. These observations indicate that the resonant electrons in an anisotropic pitch angle distribution mainly undergo the rapid pitch angle scattering loss during the wave-particle resonances.

The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons

“…However, our statistical results indicate that the spatial range of the butterfly pitch angle distributions is inconsistent with that of the magnetosonic waves shown by Ma et al []. Moreover, the energy‐independent butterfly distributions are different from the energy‐dependent pitch angle scatterings driven by other plasma waves [ Li et al , ].…”

Energetic electron bursts in the plasma sheet and their relation with BBFs

“…On one hand, the strong dawn‐dusk magnetic field drift may make some energetic electrons escape from the dawnward edge of flow channel. On the other hand, the pitch angle scattering caused by whistler mode waves within BBFs may make some energetic electrons drop into loss cone [ Liang et al ., ; Li et al ., ; Panov et al ., ]. The dawn‐dusk electric field in Figure f has two similar increase phases, which correspond well to the gradual increase phase and the rapid increase phase of EEB in Figure a.…”

Propagation characteristics of plasmaspheric hiss: Van Allen Probe observations and global empirical models

“…The extremely low frequency (ELF) hiss waves are probably amplified through the cyclotron resonance with anisotropic suprathermal electrons or the penetration of whistler mode chorus waves [ Meredith et al ., ; Bortnik et al ., ; Chen et al ., ; Zhima et al ., ; Li et al ., ]. Since whistler mode hiss waves can scatter relativistic electrons (>0.5 MeV) into the loss cone [ Summers et al ., , ; Cao et al ., ; Xiao et al ., ; L. Y. Li et al ., , ; Tu et al ., ], they are often used to account for the relativistic electron loss in the slot region (L ~ 2–3) [ Lyons et al ., ; Meredith et al ., ]. Moreover, plasmaspheric hiss can also cause the slow decay of an unusual narrow ring of relativistic electrons near L ~ 3.2 [ Thorne et al ., ].…”