Comparative Study of the Solar Wind: Modeling Charge State Distributions in the Heliosphere

Non-equilibrium ionization (NEI) is a key process often times ignored when modeling astrophysical plasmas whose thermodynamical timescales are much shorter than the timescales for ionization and recombination. In this paper, we use magnetohydrodynamics (MHD) models alongside numerical NEI simulations to calculate synthetic charge state distributions during the Whole Sun Month interval (CR)-1913 (1996, 22 August to 1996, 18 September), and compare them with in-situ measurements made with the Ulysses Solar Wind Ion Spectrometer Composition (SWICS) instrument. The key ndings of our analysis have: (1) shown that the solar wind speeds at 20 R_s calculated by the Magnetohydrodynamics Around a Sphere (MAS) model were not in agreement with the Ulysses observations; (2) measured the "freeze-in" distance for each ion observed by the SWICS instrument to determine a possible correlation between when the ionization states become fixed and their expansion into the solar wind; (3) shown how di erent charge state densities and abundance ratios compared with observation.