Observational evidence for solar wind proton heating by ion-scale turbulence

TL;DR

This study provides observational evidence that proton-scale turbulence in the solar wind is linked to proton heating, revealing a scale-dependent relationship between turbulence properties and proton temperatures based on in-situ measurements.

Contribution

It is the first to demonstrate a clear scale-dependent connection between proton temperatures and turbulence in the solar wind using extensive in-situ data.

Findings

Positive correlation between proton perpendicular temperature and magnetic energy at proton scales.

Steeper magnetic energy spectra associated with higher turbulence helicity.

Evidence supporting proton-scale turbulence as a mechanism for solar wind heating.

Abstract

Based on in-situ measurements by Wind spacecraft from 2005 to 2015, this letter reports for the first time a clearly scale-dependent connection between proton temperatures and the turbulence in the solar wind. A statistical analysis of proton-scale turbulence shows that increasing helicity magnitudes correspond to steeper magnetic energy spectra. In particular, there exists a positive power-law correlation (with a slope $\sim 0.4$) between the proton perpendicular temperature and the turbulent magnetic energy at scales $0.3 \lesssim k\rho_p \lesssim 1$, with $k$ being the wavenumber and $\rho_p$ being the proton gyroradius. These findings present evidence of solar wind heating by the proton-scale turbulence. They also provide insight and observational constraint on the physics of turbulent dissipation in the solar wind.