Dependence of Ion Temperatures on Alpha–Proton Differential Flow Vector and Heating Mechanisms in the Solar Wind

摘要: According to \emph{Wind} observations between June 2004 and May 2019, this Letter investigates the proton alpha particle temperatures in space of ($\theta_d$, $V_d/V_A$) for first time, where $\theta_d$ $V_d$ are radial angle magnitude alpha$-$proton differential flow vector respectively, $V_A$ is local Alfven speed. Results show that significantly depend on as well $V_d/V_A$. In case low parallel beta ($\beta_{p{\parallel}} < 1$), it found perpendicular temperature clearly enhanced when small ($\lesssim 45^\circ$) $V_d/V_A \gtrsim 0.5$. On contrary, particles considerably large ($\gtrsim 90^\circ$) or $V_d/V_A$ sufficiently small. The maximum takes place at $\theta_d \sim 90^\circ$ accompanied by higher $\beta_{p{\parallel}}$ larger turbulence amplitude magnetic fluctuations inertial range. This study should present strong evidence cyclotron resonance heating protons solar wind. Other mechanisms including Landau stochastic also proposed, which tend have different spaces than heating.