Journal Article

Electron Dynamics Associated With Advection and Diffusion in Self‐Consistent Wave‐Particle Interactions With Oblique Chorus Waves

Chen, Lunjin, Wang, Xueyi, Lin, Yu, Chen, Huayue, Hsieh, Yi‐Kai, Omura, Yoshiharu, Chen, Rui, Zhao, Hong

2024

Overview

Chorus waves are intense electromagnetic emissions critical in modulating electron dynamics. In this study, we perform two‐dimensional particle‐in‐cell simulations to investigate self‐consistent wave‐particle interactions with oblique chorus waves. We first analyze the electron dynamics sampled from cyclotron and Landau resonances with waves, and then quantify the advection and diffusion coefficients through statistical studies. It is found that phase‐trapped cyclotron resonant electrons satisfy the second‐order resonance condition and gain energy from waves. While phase‐bunched cyclotron resonant electrons cannot remain in resonance for long periods. They transfer energy to waves and are scattered to smaller pitch angles. Landau resonant electrons are primarily energized by waves. For both types of resonances, advection coefficients are greater than diffusion coefficients when the wave amplitude is large. Our study highlights the important role of advection in electron dynamics modulation resulting from nonlinear wave‐particle interactions. Plain Language Summary Wave‐particle interactions can modulate electron distributions through advection and diffusion. Previous studies focusing on advection and diffusion primarily relied on test particle simulations, which uses a simplified model of wave evolution. In this study, we perform self‐consistent simulations to investigate the wave‐particle interactions with chorus waves and quantify the advection and diffusion coefficients of resonant electrons. It is found that advection coefficients are greater than diffusion coefficients in both cyclotron and Landau resonances, indicating the significant role of nonlinear wave‐particle interactions. The quantification of advection and diffusion coefficients in a self‐consistent system is important for understanding and predicting the loss and energization processes in radiation belt electrons. This study complements previous diffusion models that regarded the evolution of electron dynamics in wave‐particle interactions as a slow diffusive process. Key Points Electron advection and diffusion in wave‐particle interactions with chorus waves are investigated through self‐consistent simulations The second‐order time derivative of gyrophase angle is nearly zero for phase‐trapped electrons but is negative for phase‐bunched electrons The advection and diffusion coefficients for cyclotron and Landau resonant electrons interacting with chorus waves are quantified

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Advection / advection and diffusion coefficients / Chorus waves / cyclotron and Landau resonances / Cyclotron resonance / Diffusion / Diffusion coefficient / Diffusion coefficients / Diffusion models / Diffusion rate / Dynamics / electron dynamics / Electrons / Evolution / Nonlinear dynamics / Nonlinear waves / Particle interactions / Pitch (inclination) / Radiation belt electrons / Radiation belts / Resonance / Resonance scattering / self‐consistent particle‐in‐cell simulations / Simulation / Wave amplitude / Waves / wave‐particle interaction in chorus waves