Proton Heating in Solar Wind Compressible Turbulence with Collisions between Counter-propagating Waves

Abstract

Magnetohydronamic turbulence is believed to play a crucial role in heating the laboratorial, space, and astrophysical plasmas. However, the precise connection between the turbulent fluctuations and the particle kinetics has not yet been established. Here we present clear evidence of plasma turbulence heating based on diagnosed wave features and proton velocity distributions from solar wind measurements by the Wind spacecraft. For the first time, we can report the simultaneous observation of counter-propagating magnetohydrodynamic waves in the solar wind turbulence. Different from the traditional paradigm with counter-propagating Alfvén waves, anti-sunward Alfvén waves (AWs) are encountered by sunward slow magnetosonic waves (SMWs) in this new type of solar wind compressible turbulence. The counter-propagating AWs and SWs correspond respectively to the dominant and sub-dominant populations of the imbalanced Elsässer variables. Nonlinear interactions between the AWs and SMWs are inferred from the non-orthogonality between the possible oscillation direction of one wave and the possible propagation direction of the other. The associated protons are revealed to exhibit bi-directional asymmetric beams in their velocity distributions: sunward beams appearing in short and narrow patterns and anti-sunward broad extended tails. It is suggested that multiple types of wave-particle interactions, i.e., cyclotron and Landau resonances with AWs and SMWs at kinetic scales, are taking place to jointly heat the protons perpendicularly and parallel.

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• Scale dependence of energy transfer in turbulent plasma
• Colliding Alfvénic wave packets in MHD, Hall and kinetic simulations
• Revisiting a classic: the Parker-Moffatt problem
• Magnetospheric Multiscale Observation of Kinetic Signatures in the Alfvén Vortex
• The Parametric Decay Instability of Alfven waves in Turbulent Plasmas and the Applications in the Solar Wind
• Possible Generation Mechanism for Compressional Alfvénic Spikes as Observed by Parker Solar Probe
• Statistical analysis of intermittency and its association with proton heating in the near Sun environment
• Solar wind collisional heating
• Multi-scale Pressure-balanced Structures in Three-dimensional Magnetohydrodynamic Turbulence
• Kinetic Simulation of Slow Magnetosonic Waves and Quasi-periodic Upflows in the Solar Corona
• Sunward-propagating Alfvénic fluctuations observed in the heliosphere
• Magnetic Energy Transfer and Distribution between Protons and Electrons for Alfvénic Waves at Kinetic Scales in Wavenumber Space
• Effect of the electronic pressure on the energy and magnetic moment of charged test particles in turbulent electromagnetic fields