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Journal Articles The Astrophysical Journal Supplement Year : 2020

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

Justin Kasper
Anthony Case
Kelly Korreck
Davin Larson
Roberto Livi
Michael Stevens
Benjamin Chandran
  • Function : Author
Ben Alterman
  • Function : Author
Jia Huang
Christopher Chen
  • Function : Author
Stuart Bale
Marc Pulupa
David Malaspina
John Bonnell
Peter Harvey
Keith Goetz
Robert Macdowall


Stochastic heating (SH) is a nonlinear heating mechanism driven by the violation of magnetic moment invariance due to large-amplitude turbulent fluctuations producing diffusion of ions toward 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 SH rate Q(perpendicular to) 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(perpendicular to) proportional to 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(perpendicular to) 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 flattop shape. The observed distribution agrees with previous theoretical predictions for fast solar wind where SH is the dominant heating mechanism.

Dates and versions

insu-02937640 , version 1 (14-09-2020)



Mihailo Martinović, Kristopher Klein, Justin Kasper, Anthony Case, Kelly Korreck, et al.. The Enhancement of Proton Stochastic Heating in the Near-Sun Solar Wind. The Astrophysical Journal Supplement, 2020, 246 (2), pp.30. ⟨10.3847/1538-4365/ab527f⟩. ⟨insu-02937640⟩
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