The Fluid-like Behavior of Kinetic Alfvén Turbulence in Space Plasma

Abstract

Kinetic Alfvén waves (KAWs) are the short-wavelength extension of the MHD Alfvén-wave branch in the case of highly-oblique propagation with respect to the background magnetic field. Observations of space plasma show that small-scale turbulence is mainly KAW-like. We apply two theoretical approaches, collisional two-fluid theory and collisionless kinetic theory, to obtain predictions for the KAW polarizations depending on ${\beta }_{\mathrm{p}}$ (the ratio of the proton thermal pressure to the magnetic pressure) at the ion gyroscale in terms of fluctuations in density, bulk velocity, and pressure. We perform a wavelet analysis of MMS magnetosheath measurements and compare the observations with both theories. We find that the two-fluid theory predicts the observations better than kinetic theory, suggesting that the small-scale KAW-like fluctuations exhibit a fluid-like behavior in the magnetosheath although the plasma is weakly collisional. We also present predictions for the KAW polarizations in the inner heliosphere that are testable with Parker Solar Probe and Solar Orbiter.

arXiv comment9 pages, 6 figures, submitted

References in corpus (18)

• Anisotropic scaling of magnetohydrodynamic turbulence
• Dependence of solar wind power spectra on the direction of the local mean magnetic field
• Anisotropy of Solar Wind Turbulence between Ion and Electron Scales
• The Nature of Subproton Scale Turbulence in the Solar Wind
• Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind
• Nature of Kinetic Scale Turbulence in the Earth's Magnetosheath
• Anisotropy of Alfvénic Turbulence in the Solar Wind and Numerical Simulations
• Three-Dimensional Structure of Solar Wind Turbulence
• Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence
• Constraining Low-Frequency Alfvenic Turbulence in the Solar Wind Using Density Fluctuation Measurements
• On Kinetic Slow Modes, Fluid Slow Modes, and Pressure-balanced Structures in the Solar Wind
• Collisionless Isotropization of the Solar-Wind Protons by Compressive Fluctuations and Plasma Instabilities
• The Violation of the Taylor Hypothesis in Measurements of Solar Wind Turbulence
• Radial evolution of the wave-vector anisotropy of solar wind turbulence between 0.3 and 1 AU
• NHDS: The New Hampshire Dispersion Relation Solver
• Suppression of phase mixing in drift-kinetic plasma turbulence
• Spectral Anisotropy of Elsässer Variables in Two Dimensional Wave-vector Space as Observed in the Fast Solar Wind Turbulence
• A linear dispersion relation for the hybrid kinetic-ion/fluid-electron model of plasma physics

Cited by in corpus (9)

• The multi-scale nature of the solar wind
• Diagnosing collisionless energy transfer using field-particle correlations: Alfven-Ion Cyclotron Turbulence
• The Impact of Turbulent Solar Wind Fluctuations on Solar Orbiter Plasma Proton Measurements
• -8/3 spectrum in kinetic Alfvén wave turbulence: implications for the solar wind
• The polytropic behavior of Solar Wind protons as observed by Ulysses spacecraft during Solar minimum
• Deriving the bulk properties of solar wind electrons observed by Solar Orbiter: A preliminary study of electron plasma thermodynamics
• Dependence of kinetic plasma waves on ion-to-electron mass ratio and light-to-Alfvén speed ratio
• On the ion-inertial range density power spectra in solar wind turbulence
• Ion-scale Turbulence and Energy Cascade Rate in the Solar Corona and Inner Heliosphere