Large-scale Control of Kinetic Dissipation in the Solar Wind

In this Letter we study the connection between the large-scale dynamics of the turbulence cascade and particle heating on kinetic scales. We find that the inertial range turbulence amplitude ($\delta B_i$; measured in the range of 0.01-0.1 Hz) is a simple and effective proxy to identify the onset of significant ion heating and when it is combined with ${\beta }_{\mathrm{\mid }\mathrm{\mid }p}$, it characterizes the energy partitioning between protons and electrons ($T_p\mathrm{/}{T}_e$), proton temperature anisotropy ($T_{\perp }\mathrm{/}{T}_{\mathrm{\mid }\mathrm{\mid }}$) and scalar proton temperature ($T_p$) in a way that is consistent with previous predictions. For a fixed $\delta B_i$, the ratio of linear to nonlinear timescales is strongly correlated with the scalar proton temperature in agreement with Matthaeus et al., though for solar wind intervals with ${\beta }_{\mathrm{\mid }\mathrm{\mid }p}>1$ some discrepancies are found. For a fixed ${\beta }_{\mathrm{\mid }\mathrm{\mid }p}$, an increase of the turbulence amplitude leads to higher $T_p\mathrm{/}{T}_e$ ratios, which is consistent with the models of Chandran et al. and Wu et al. We discuss the implications of these findings for our understanding of plasma turbulence.