The Velocity-Space Signature of Transit-Time Damping

Abstract

Transit-time damping (TTD) is a process in which the magnetic mirror force -- induced by the parallel gradient of magnetic field strength -- interacts with resonant plasma particles in a time-varying magnetic field, leading to the collisionless damping of electromagnetic waves and the resulting energization of those particles through the perpendicular component of the electric field, $E_{\perp }$. In this study, we utilize the recently developed field-particle correlation technique to analyze gyrokinetic simulation data. This method enables the identification of the velocity-space structure of the TTD energy transfer rate between waves and particles during the damping of plasma turbulence. Our analysis reveals a unique bipolar pattern of energy transfer in velocity space characteristic of TTD. By identifying this pattern, we provide clear evidence of TTD's significant role in the damping of strong plasma turbulence. Additionally, we compare the TTD signature with that of Landau damping (LD). Although they both produce a bipolar pattern of phase-space energy density loss and gain about the parallel resonant velocity of the Alfvénic waves, they are mediated by different forces and exhibit different behaviors as $v_{\perp }\to 0$. We also explore how the dominant damping mechanism varies with ion plasma beta ${\beta }_i$, showing that TTD dominates over LD for ${\beta }_i>1$. This work deepens our understanding of the role of TTD in the damping of weakly collisional plasma turbulence and paves the way to seek the signature of TTD using \emph{in situ} spacecraft observations of turbulence in space plasmas.

15 figures

References in corpus (14)

• Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas
• Evidence for Electron Landau Damping in Space Plasma Turbulence
• Linearized model Fokker-Planck collision operators for gyrokinetic simulations. I. Theory
• Predicted Impacts of Proton Temperature Anisotropy on Solar Wind Turbulence
• Measuring Collisionless Damping in Heliospheric Plasmas using Field-Particle Correlations
• Validity of the Taylor Hypothesis for Linear Kinetic Waves in the Weakly Collisional Solar Wind
• Diagnosing collisionless energy transfer using field-particle correlations: gyrokinetic turbulence
• A Prospectus on Kinetic Heliophysics
• The Dynamical Generation of Current Sheets in Astrophysical Plasma Turbulence
• Diagnosing collisionless energy transfer using field-particle correlations: Alfven-Ion Cyclotron Turbulence
• On stochastic heating and its phase-space signatures in low-$\beta$ kinetic turbulence
• The Enhancement of Proton Stochastic Heating in the near-Sun Solar Wind
• The Importance of Electron Landau Damping for the Dissipation of Turbulent Energy in Terrestrial Magnetosheath Plasma
• Kinetic Turbulence in Collisionless High-Beta Plasmas

Cited by in corpus (1)

• Unveiling the Velocity-Space Signature of Ion Cyclotron Damping Using Liouville Mapping