A Hamiltonian gyrofluid model based on a quasi-static closure

Abstract

A Hamiltonian six-field gyrofluid model is constructed, based on closure relations derived from the so-called "quasi-static" gyrokinetic linear theory where the fields are assumed to propagate with a parallel phase velocity much smaller than the parallel particle thermal velocities. The main properties of this model, primarily aimed at exploring basic phenomena of interest for space plasmas such as the solar wind, are its ability to provide a reasonable agreement with kinetic theory for linear low-frequency modes, and at the same time to ensure a Hamiltonian structure in the absence of explicit dissipation. The model accounts for equilibrium temperature anisotropy, ion and electron finite Larmor radius corrections, electron inertia, magnetic fluctuations along the direction of a strong guide field, and parallel Landau damping. Remarkably, the quasi-static closure leads to exact expressions for the nonlinear terms involving gyroaveraged electromagnetic perturbations. One of the consequences is that a rather natural identification of the Hamiltonian structure of the model becomes possible when Landau damping is neglected. A slight variant of the model consists of a four-field Hamiltonian reduction of the original six-field model, which we use for the subsequent linear analysis. In the latter, the dispersion relations of kinetic Alfvén waves and the firehose instability are shown to be correctly reproduced, relatively far in the sub-ion range (depending on the plasma parameters), while the spectral range where the slow-wave dispersion relation and the field-swelling instabilities are precisely described is less extended. This loss of accuracy originates from the breaking of the condition of small phase velocity, relative to the parallel thermal velocity of the electrons (for kinetic Alfvén waves and firehose instability) or of the ions (in the case of the field-swelling instabilities).

References in corpus (23)

• Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind
• Solar Wind Turbulence and the Role of Ion Instabilities
• Spectrum of Kinetic Alfven Turbulence
• Evidence for Electron Landau Damping in Space Plasma Turbulence
• Nature of Kinetic Scale Turbulence in the Earth's Magnetosheath
• Magnetic reconnection as a driver for a sub-ion scale cascade in plasma turbulence
• Proton Temperature Anisotropy Variations in Inner Heliosphere Estimated with First Parker Solar Probe Observations
• Inertial-Range Kinetic Turbulence in Pressure-Anisotropic Astrophysical Plasmas
• Observational Test of Stochastic Heating in Low-$\beta$ Fast Solar Wind Streams
• Laguerre-Hermite Pseudo-Spectral Velocity Formulation of Gyrokinetics
• Astrophysical gyrokinetics: Turbulence in pressure-anisotropic plasmas at ion scales and beyond
• A model for the non-universal power-law of the solar wind sub-ion scale magnetic spectrum
• Density Fluctuations in the Solar Wind Driven by Alfvén Wave Parametric Decay
• Fluid and gyrofluid modeling of low-${\beta }_e$ plasmas: phenomenology of kinetic Alfvén wave turbulence
• The parametric instability of Alfvén waves: effects of temperature anisotropy
• Stochastic proton heating by kinetic-Alfvén-wave turbulence in moderately high-$\beta$ plasmas
• An introductory guide to fluid models with anisotropic temperatures Part 2 -- Kinetic theory, Padé approximants and Landau fluid closures
• Electron-scale reduced fluid models with gyroviscous effects
• Imbalanced kinetic Alfvén wave turbulence: from weak turbulence theory to nonlinear diffusion models for the strong regime
• Proton temperature anisotropy and magnetic reconnection in the solar wind: effects of kinetic instabilities on current sheet stability
• A Hamiltonian Five-Field Gyrofluid Model
• Pressure anisotropy generation in a magnetized plasma configuration with a shear flow velocity
• Modeling imbalanced collisionless Alfvén wave turbulence with nonlinear diffusion equations

Cited by in corpus (5)

• Inverse cascade and magnetic vortices in kinetic Alfvén-wave turbulence
• Gyrofluid simulations of turbulence and reconnection in space plasmas
• Investigation of the collisionless plasmoid instability based on gyrofluid and gyrokinetic integrated approach
• ALLIANCE: Spectral solver for kinetic plasma turbulence
• Impact of electron temperature anisotropy on the collisionless tearing mode instability in the presence of a strong guide field