MHD-kinetic transition in imbalanced Alfvénic turbulence

Abstract

Alfvénic turbulence in space is usually imbalanced: amplitudes of waves propagating parallel and anti-parallel to the mean magnetic field $B_0$ are unequal. It is commonly accepted that the turbulence is driven by (counter-)collisions between these counter-propagating wave fractions. Contrary to this, we found a new ion-scale dynamical range of the turbulence established by (co-)collisions among waves co-propagating in the same direction along $B_0$. Co-collisions become stronger than counter-collisions and produce steep non-universal spectra above certain wavenumbers dependent on the imbalance. Spectral indexes of the strong turbulence vary around -3, such that steeper spectra follow larger imbalances. Intermittency steepens the -3 spectra further, up to -3.7. Our theoretical predictions are compatible with steep variable spectra observed in the solar wind at ion kinetic scales, but further verifications are needed by correlating observed spectra with measured imbalances.

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• Anisotropy of Solar-Wind Turbulence in the Inner Heliosphere at Kinetic Scales: PSP Observations
• Inner-Heliosphere Signatures of Ion-Scale Dissipation and Nonlinear Interaction
• Kinetic Turbulence in Astrophysical Plasmas: Waves and/or Structures?
• The Ion Transition Range of Solar Wind Turbulence in the Inner Heliosphere: Parker Solar Probe Observations
• Imbalanced kinetic Alfvén wave turbulence: from weak turbulence theory to nonlinear diffusion models for the strong regime
• Kinetic range spectral features of cross-helicity using MMS
• Solar wind magnetic field background spectrum from fluid to kinetic scales
• Modeling imbalanced collisionless Alfvén wave turbulence with nonlinear diffusion equations
• Kinetic Simulations of Imbalanced Turbulence in a Relativistic Plasma: Net Flow and Particle Acceleration
• Solar plasma radio emission in the presence of imbalanced turbulence of kinetic-scale Alfvén waves
• Direct kinetic Alfvén wave energy cascade in the presence of imbalance
• The effects of finite electron inertia on helicity-barrier-mediated turbulence
• Gyrofluid simulations of turbulence and reconnection in space plasmas
• Turbulent heating in collisionless low-beta plasmas: imbalance, Landau damping, and electron-ion energy partition