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

Mihailo M. Martinović, Kristopher G. Klein, Justin C. Kasper, Anthony W. Case, Kelly E. Korreck, Davin Larson, Roberto Livi, Michael Stevens, Phyllis Whittlesey, Benjamin D.G. Chandran, Ben L. Alterman, Jia Huang, Christopher H.K. Chen, Stuart D. Bale, Marc Pulupa, David M. Malaspina, John W. Bonnell, Peter R. Harvey, Keith Goetz, Thierry Dudok De WitRobert J. MacDowall

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


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 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 ∝ 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 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.

Original languageEnglish (US)
Article number30
JournalAstrophysical Journal, Supplement Series
Issue number2
StatePublished - Feb 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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