The Enhancement of Proton Stochastic Heating in the near-Sun Solar Wind

Abstract

Stochastic heating is a non-linear heating mechanism driven by the violation of magnetic moment invariance due to large-amplitude turbulent fluctuations producing diffusion of ions towards higher kinetic energies in the direction perpendicular to the magnetic field. It is frequently invoked as a mechanism responsible for the heating of ions in the solar wind. Here, we quantify for the first time the proton stochastic heating rate $Q_{\perp }$ at radial distances from the Sun as close as $0.16$ au, using measurements from the first two Parker Solar Probe encounters. Our results for both the amplitude and radial trend of the heating rate, $Q_{\perp }\propto r^{-2.5}$, agree with previous results based on the Helios data set at heliocentric distances from 0.3 to 0.9 au. Also in agreement with previous results, $Q_{\perp }$ is significantly larger in the fast solar wind than in the slow solar wind. We identify the tendency in fast solar wind for cuts of the core proton velocity distribution transverse to the magnetic field to exhibit a flat-top shape. The observed distribution agrees with previous theoretical predictions for fast solar wind where stochastic heating is the dominant heating mechanism.

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Cited by in corpus (19)

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• On stochastic heating and its phase-space signatures in low-$\beta$ kinetic turbulence
• Multiscale Solar Wind Turbulence Properties inside and near Switchbacks measured by Parker Solar Probe
• Flux rope merging and the structure of switchbacks in the solar wind
• Energy Supply for Heating the Slow Solar Wind Observed by Parker Solar Probe between 0.17 and 0.7 au
• Proton and electron temperatures in the solar wind and their correlations with the solar wind speed
• Estimation of turbulent proton and electron heating rates via Landau damping constrained by Parker Solar Probe observations
• Phase-space entropy cascade and irreversibility of stochastic heating in nearly collisionless plasma turbulence
• Magnetic helicity signature and its role in regulating magnetic energy spectra and proton temperatures in the solar wind
• The Velocity-Space Signature of Transit-Time Damping
• On the transition from Slow to Fast Wind as Observed in Composition Observations
• A Unified Phenomenology of Ion Heating in Low-$\beta$ Plasmas: Test-Particle Simulations
• Effects of the Background Turbulence on the Relaxation of Ion Temperature Anisotropy in Space Plasmas
• Thresholdless stochastic particle heating by a single wave
• Does Turbulence along the Coronal Current Sheet Drive Ion Cyclotron Waves?
• Anisotropic electron heating in turbulence-driven magnetic reconnection in the near-Sun solar wind