  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.
