Electron Distributions in Kinetic Scale Field Line Resonances: A Comparison of Simulations and Observations

Abstract

Observations in kinetic scale field line resonances, or eigenmodes of the geomagnetic field, reveal highly field‐aligned plateaued electron distributions. By combining observations from the Van Allen Probes and Cluster spacecraft with a hybrid kinetic gyrofluid simulation we show how these distributions arise from the nonlocal self‐consistent interaction of electrons with the wavefield. This interaction is manifested as electron trapping in the standing wave potential. The process operates along most of the field line and qualitatively accounts for electron observations near the equatorial plane and at higher latitudes. In conjunction with the highly field‐aligned plateaus, loss cone features are also evident, which result from the action of the upward‐directed wave parallel electric field on the untrapped electron populations.

Charged particle nonlinear resonance with localized electrostatic wave-packets

“…Third, kinetic Alfven waves accelerate low-energy particles and enhance the population of ∼ 100 − 300 eV electrons. Such enhancements were found before in selfconsistent models of kinetic Alfven waves [45,87]. Therefore, our simulation demonstrates that the proposed approach can be applied for description of realistic space plasma systems.…”

“…The Landau resonance of nonrelativistic electrons and localized wave packets of oblique whistler waves, electron acoustic waves, and kinetic Alfven waves represent an important example of nonrelativistic electron acceleration in the near-Earth plasma environment. These three wave modes are exited at the fast plasma flows penetrating the inner Earth magnetosphere [14,[82][83][84] and can significantly affect the thermal electrons transported by these flows [85][86][87]. Electron acoustic waves represent purely electrostatic wave mode [88]; kinetic Alfven waves and very oblique whistler waves are electromagnetic modes, but these waves carry a significant field-aligned electric field that resonate with electrons (and such resonant interaction is described by Hamiltonian (4), see details in [44,89]).…”

Correlations Between Dispersive Alfvén Wave Activity, Electron Energization, and Ion Outflow in the Inner Magnetosphere

“…However, while field‐aligned electron distributions are always observed in DAWs, TDS are not. Moreover, kinetic simulations demonstrate that DAW activity alone can reproduce observed energies and distribution features (Damiano et al, 2018). A description of electron acceleration processes in TDS is provided by Vasko et al (2017).…”

Kinetic Simulations of Electron Acceleration by Dispersive Scale Alfvén Waves in Jupiter's Magnetosphere

“…In the present work, we do not consider the cross‐scale coupling of wave energy but assume the existence of small‐scale Alfvén perturbations in the Io plasma torus and for the first time (in kinetic simulation) self‐consistently follow the evolution of the interaction between the Alfvén waves and electrons from this source region to the high latitudes. For this investigation we use the Gyrofluid‐Kinetic‐Electron (GKE) model (Damiano et al, ), which has also been used for the study of electron energization in both large‐scale (Damiano & Wright, ; Damiano & Johnson, ) and dispersive scale (Damiano et al, ; ; Damiano et al, ) Alfvén waves in the terrestrial magnetosphere. The remainder of the paper is divided into three sections.…”