Empirical Modeling of the Fast Solar Wind

Abstract In this work we derive empirical models of the fast solar wind by applying a Monte Carlo Markov Chain technique to in situ measurements of the wind charge state distributions to determine the wind’s electron temperature, electron density, and bulk speed from the source region to the freeze-in point. We utilize 6 month averages of ACE/SWICS measurements carried out at seven different times along the solar cycle, to monitor whether the solar cycle causes any changes in the results. We use the results to estimate several wind plasma properties as well as the wave pressure and energy needed to power the solar wind in the 1-temperature wind model by S. R. Cranmer et al. We find that the bulk of the momentum and energy is injected between 1.5 and 3.0 solar radii and that the solar cycle does not qualitatively affect the results. However, the plasma acceleration predicted by our empirical model occurs much closer to the Sun than indicated by SoHO/UVCS measurements: we discuss this discrepancy as well as other approximations and limitations of the present work.