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

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.

15 pages, 4 figures, accepted for publication in Geophysical Research Letters

References in corpus (9)

• Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas
• Wave turbulence in incompressible Hall MHD
• Ion Scale Electromagnetic Waves in the Inner Heliosphere
• Spectral Slope Variation at Proton Scales from Fast to Slow Solar Wind
• Physical Interpretation of the Angle Dependent Magnetic Helicity Spectrum in the Solar Wind: The Nature of Turbulent Fluctuations near the Proton Gyroradius Scale
• The Radial Dependence of Proton-scale Magnetic Spectral Break in Slow Solar Wind during PSP Encounter 2
• Magnetospheric Multiscale Observation of Kinetic Signatures in the Alfvén Vortex
• Linking Fluid and Kinetic Scales in Solar Wind Turbulence
• Dependence of ion temperatures on alpha-proton differential flow vector and heating mechanisms in the solar wind