A Quasi-Linear Diffusion Model for Resonant Wave-Particle Instability in Homogeneous Plasma

Abstract

In this paper, we develop a model to describe the generalized wave-particle instability in a quasi-neutral plasma. We analyze the quasi-linear diffusion equation for particles by expressing an arbitrary unstable and resonant wave mode as a Gaussian wave packet, allowing for an arbitrary direction of propagation with respect to the background magnetic field. We show that the localized energy density of the Gaussian wave packet determines the velocity-space range in which the dominant wave-particle instability and counter-acting damping contributions are effective. Moreover, we derive a relation describing the diffusive trajectories of resonant particles in velocity space under the action of such an interplay between the wave-particle instability and damping. For the numerical computation of our theoretical model, we develop a mathematical approach based on the Crank-Nicolson scheme to solve the full quasi-linear diffusion equation. Our numerical analysis solves the time evolution of the velocity distribution function under the action of a dominant wave-particle instability and counteracting damping and shows a good agreement with our theoretical description. As an application, we use our model to study the oblique fast-magnetosonic/whistler instability, which is proposed as a scattering mechanism for strahl electrons in the solar wind. In addition, we numerically solve the full Fokker-Planck equation to compute the time evolution of the electron-strahl distribution function under the action of Coulomb collisions with core electrons and protons after the collisionless action of the oblique fast-magnetosonic/whistler instability.

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Cited by in corpus (13)

• Precision Electron Measurements in the Solar Wind at 1 au from NASA's Wind Spacecraft
• On the role of solar wind expansion as a source of whistler waves: scattering of suprathermal electrons and heat flux regulation in the inner heliosphere
• General dispersion properties of magnetized plasmas with drifting bi-Kappa distributions. DIS-K: DIspersion Solver for Kappa plasmas
• Whistler Waves As a Signature of Converging Magnetic Holes in Space Plasmas
• A new low-beta regime for unstable proton firehose modes in bi-Kappa distributed plasmas
• Thermal energy budget of electrons in the inner heliosphere: Parker Solar Probe Observations
• The Stability of the Electron Strahl against the Oblique Fast-magnetosonic/Whistler Instability in the Inner Heliosphere
• The Kinetic Expansion of Solar-Wind Electrons: Transport Theory and Predictions for the very Inner Heliosphere
• Stochastic diffusion of electrons interacting with whistler-mode waves in the solar wind
• A Kinetic Model of Solar Wind Acceleration Driven by Ambipolar Electric Potential and Velocity-Space Diffusion
• Quasi-parallel anti-sunward propagating whistler waves associated to the electron-deficit in the near-Sun solar wind: Particle-in-Cell simulation
• The Wave Energy Density and Growth Rate for the Resonant Instability in Relativistic Plasmas
• Ambipolar electric field and potential in the solar wind estimated from electron velocity distribution functions