The In Situ Signature of Cyclotron Resonant Heating

Abstract

The dissipation of magnetized turbulence is an important paradigm for describing heating and energy transfer in astrophysical environments such as the solar corona and wind; however, the specific collisionless processes behind dissipation and heating remain relatively unconstrained by measurements. Remote sensing observations have suggested the presence of strong temperature anisotropy in the solar corona consistent with cyclotron resonant heating. In the solar wind, in situ magnetic field measurements reveal the presence of cyclotron waves, while measured ion velocity distribution functions have hinted at the active presence of cyclotron resonance. Here, we present Parker Solar Probe observations that connect the presence of ion-cyclotron waves directly to signatures of resonant damping in observed proton-velocity distributions. We show that the observed cyclotron wave population coincides with both flattening in the phase space distribution predicted by resonant quasilinear diffusion and steepening in the turbulent spectra at the ion-cyclotron resonant scale. In measured velocity distribution functions where cyclotron resonant flattening is weaker, the distributions are nearly uniformly subject to ion-cyclotron wave damping rather than emission, indicating that the distributions can damp the observed wave population. These results are consistent with active cyclotron heating in the solar wind.

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Cited by in corpus (11)

• The Radial Distribution of Ion-scale Waves in the Inner Heliosphere
• Electron-ion heating partition in imbalanced solar-wind turbulence
• Fully Kinetic Simulations of Proton-Beam-Driven Instabilities from Parker Solar Probe Observations
• Identification of coupled Landau and anomalous resonances in space plasmas
• A Unified Phenomenology of Ion Heating in Low-$\beta$ Plasmas: Test-Particle Simulations
• Direct kinetic Alfvén wave energy cascade in the presence of imbalance
• The effects of finite electron inertia on helicity-barrier-mediated turbulence
• Does Turbulence along the Coronal Current Sheet Drive Ion Cyclotron Waves?
• Gyrofluid simulations of turbulence and reconnection in space plasmas
• Turbulent heating in collisionless low-beta plasmas: imbalance, Landau damping, and electron-ion energy partition
• Stability of Parker's Solar Wind Solution Near the Solar Surface