Bounce Resonance Scattering of Radiation Belt Energetic Electrons by Extremely Low‐Frequency Chorus Waves

Abstract

Whistler-mode chorus waves are one of the most important and common waves in the Earth's magnetosphere with the frequencies generally ranging from 0.1 f ce to 0.8 f ce (f ce is the electron gyro-frequency). By the gap around 0.5 f ce , chorus waves are divided into upper band (0.5 f ce < f < 0.8 f ce ) and lower band (0.1 f ce < f < 0.5 f ce ) (W.

Long‐Term Variations of Energetic Electrons Scattered by Signals From the North West Cape Transmitter

“…The cyclotron resonance between magnetospheric plasma waves and energetic particles drives PA diffusion of electrons and is an important loss mechanism of radiation belt electrons (e.g., Shen et al., 2022; Shprits et al., 2006; Thorne, 2010; Xiao et al., 2009; Zhao et al., 2022). Several wave modes can scatter energetic electrons, such as chorus wave, hiss wave, EMIC wave, and artificial VLF transmitter signals (Albert et al., 2020; Cao et al., 2017; Guo et al., 2021; Meredith et al., 2007, 2009; Ni et al., 2014, 2015, 2017, 2022; Sauvaud et al., 2008; Selesnick et al., 2013; Wang et al., 2022; Xiang et al., 2018; Xiang, Li, Ni, et al, 2020; Zhang et al., 2016; Zhao et al., 2019; Zhu et al., 2021). The general condition of wave‐particle cyclotron resonance is listed as follows (Thorne, 2010): $$$\begin{array}{c}\omega -{k}_{{\Vert} }{v}_{{\Vert} }=\frac{N{{\Omega }}_{e}}{\gamma }\,\end{array}$$$ where ω is the wave frequency (the center frequency of NWC transmitter signals is 19.8 kHz), k ∥ and v ∥ are the components of the wave number and the electron velocity parallel to the background magnetic field line, N is the harmonic resonance number, Ω e is the electron gyrofrequency, and γ is the relativistic Lorentz factor.…”

“…The cyclotron resonance between magnetospheric plasma waves and energetic particles drives PA diffusion of electrons and is an important loss mechanism of radiation belt electrons (e.g., Shen et al, 2022;Shprits et al, 2006;Thorne, 2010;Xiao et al, 2009;Zhao et al, 2022). Several wave modes can scatter energetic electrons, such as chorus wave, hiss wave, EMIC wave, and artificial VLF transmitter signals (Albert et al, 2020;Cao et al, 2017;Guo et al, 2021;Meredith et al, 2007Meredith et al, , 2009Ni et al, 2014Ni et al, , 2015Ni et al, , 2017Ni et al, , 2022Sauvaud et al, 2008;Selesnick et al, 2013;Wang et al, 2022;Xiang et al, 2018;Zhang et al, 2016;Zhao et al, 2019;Zhu et al, 2021). The general condition of wave-particle cyclotron resonance is listed as follows (Thorne, 2010):…”

Ultra-relativistic Electron Acceleration during High-intensity Long-duration Continuous Auroral Electrojet Activity Events

“…In this mechanism, diffusion of electrons from the outer magnetosphere with weak magnetic fields to the inner magnetosphere with stronger magnetic fields results in betatron and Fermi accelerations of the electrons (Alfvén 1950;Fälthammar 1965;Schulz & Lanzerotti 1974;Elkington et al 1999;Hudson et al 1999;Li & Temerin 2001;Mann et al 2004;Miyoshi et al 2004). Earlier works have demonstrated case-to-case variations in the dominant roles played by radial diffusion (Zong et al 2009;Ali et al 2016;Jaynes et al 2018;Ozeke et al 2020) and local acceleration (Thorne 2010;Reeves et al 2013;Thorne et al 2013;Li et al 2014;Xiao et al 2014;Allison & Shprits 2020;Guo et al 2021). The combined impacts of both the mechanisms (Baker et al 2014;Zhao et al 2019;Guo et al 2023) and energy-dependent acceleration mechanisms (Foster et al 2014;Kanekal et al 2015;Li et al 2016;Zhao et al 2018) have also been discussed.…”

Three‐Dimensional Simulations of Ultra‐Relativistic Electron Acceleration During the 21 April 2017 Storm

“…Inward radial diffusion caused by the drift resonance between electrons and ultra‐low‐frequency (ULF) waves violates the third adiabatic invariant while the first and second adiabatic invariants are conserved, leading to increases of electron energies and pitch angles (Ali et al., 2016; W. Liu et al., 2016; Ozeke et al., 2014, 2020; Zong et al., 2009). The other acceleration mechanism is energy diffusion induced by cyclotron resonances between chorus waves and seed electrons (Allison & Shprits, 2020; D. Guo, Xiang, et al., 2021; Reeves et al., 2013; Thorne, 2010; Wang & Shprits, 2019; Xiao et al., 2014). Many observational analyses and simulation studies have verified the importance of the two mechanisms (e.g., Allison & Shprits, 2020; W. Li et al., 2016; Q. Ma et al., 2018; Reeves et al., 2013; Thorne et al., 2013; Zhao et al., 2018, 2019).…”