Radial evolution of stochastic heating in low-$\beta$ solar wind

Abstract

We consider the radial evolution of perpendicular ion heating due to the violation of magnetic moment conservation caused by Alfven and kinetic Alfven wave turbulence. This process, referred to as stochastic heating, can be quantified by the ratio between the average velocity fluctuations at the ion gyroradius and the perpendicular ion thermal speed $\epsilon \equiv \delta v/v_{t\perp }$. Using 17 years of Helios observations, we constrain how much energy could be dissipated by this mechanism between 0.29 and 0.98 au. We find that stochastic heating likely operates throughout the entire inner heliosphere, but that its radial dependence is steeper than that of empirically derived dissipation rates, being $r^{-2.5}$ compared with $r^{-2.08}$. This difference is significantly increased in fast solar wind streams to $r^{-3.1}$ compared with $r^{-1.8}$.

References in corpus (6)

• Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas
• Evidence for Electron Landau Damping in Space Plasma Turbulence
• Measuring Collisionless Damping in Heliospheric Plasmas using Field-Particle Correlations
• Diagnosing collisionless energy transfer using field-particle correlations: gyrokinetic turbulence
• A zone of preferential ion heating extends tens of solar radii from Sun
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Cited by in corpus (4)

• The Enhancement of Proton Stochastic Heating in the near-Sun Solar Wind
• The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2
• Proton and electron temperatures in the solar wind and their correlations with the solar wind speed
• Dependence of ion temperatures on alpha-proton differential flow vector and heating mechanisms in the solar wind