Transition region, corona, and solar wind in coronal holes: Some two‐fluid models

We consider the possibility that the heating of the corona and the heating and acceleration of the solar wind can be described by a single process, namely, the turbulent dissipation of solar‐generated Alfven waves at the Kolmogorov rate. The model assumes that T e = T p in r ≤ 2 R s but drops electron‐proton coupling in r > 2 R s . The dissipated wave energy is assumed to heat only the protons. Classical heat conduction is used in r ≤ 10 R s , and an electron polytrope is used in r > 10 R s . The models have the right qualitative features: a steep temperature rise to T > 10 6 K and acceleration to supersonic speeds. But models with base pressures n e T > 2×10 14 (cgs) are too slow: υ(1 AU) < 280 km s −1 . Models with υ(1 AU) > 400 km s −1 have lower base pressures: 10 14 < n e T < 2×10 14 (cgs). A difficulty with the model is that line‐of‐sight proton random velocities (thermal plus wave) are larger than values deduced from Lyman α resonant scattering observations in 1.5 ≤ r/R s ≤ 4, and they do not fall off with r to the extent observed. The large random velocities are due in part to a proton temperature peak at r ≈ 3–4 R s . On the whole, this model seems unsatisfactory, but several possible resolutions are discussed.