Proton thermal energetics in the solar wind: Helios reloaded

摘要: [1] The proton thermal energetics in the slow solar wind between 0.3 and 1 AU is reinvestigated using Helios 2 data, complementing a similar analysis for fast [Hellinger et al., 2011]. The results winds are compared discussed context of previous results. Protons need to be heated perpendicular direction with respect ambient magnetic field from AU. In parallel direction, protons cooled at AU, cooling rate comparable corresponding heating rate; required decreases until transition occurs: by require heating, that sustain temperature. heating/cooling rates (per unit volume) proportional ratio kinetic energy expansion time. On average, necessary cascade magnetohydrodynamic turbulence estimated stationary Kolmogorov-Yaglom law AU; however, expanding wind, stationarity assumption this questionable. turbulent may explain average (although needs justified) but likely related microinstabilities connected structure velocity distribution function. This supported linear based on observed data numerical simulations.