Thermal properties of the solar wind plasma

In the solar wind, electrostatic ion cyclotron waves can be excited by electrons when the flow velocity becomes supersonic. The waves reduce the proton temperature anisotropy and heat the protons effectively. Temperature equations for T _e ,T _p and T _p are solved numerically in the region from 1 AU to the Sun, with the non-thermal proton heating rate included as a parameter. Distributions of T _e ,T _p , T _p and the proton heating rate are determined and found to be in good agreement with the proton heating rate expected from the linear growth rate of electrostatic ion cyclotron waves. The electron thermal conductivity is reduced approximately 2–3 times smaller than the usual collisional one due to the plasma wave instabilities. Effective energy exchange rates from proton-proton and electron-proton interactions are 1–10 and 10–100 times larger than the Coulomb collision rates v ppand v ep,respectively.