Pickup Ion Production and Turbulence in the Global Heliosphere

The outer heliosphere model in the Space Weather Modeling Framework describes the dynamics of the thermal solar wind, pickup ions, electrons, and neutrals. We have extended this model with turbulence transport and a kinetic description of the pickup ions (PUIs) to better capture the interaction of the solar wind with the interstellar medium. The turbulence energy is enhanced via the isotropization of newly born PUIs. This increased turbulence can further heat the thermal protons and electrons. Additionally, the PUIs are nonthermal. We assume that the PUIs are fast pitch-angle scattered into isotropic distribution through wave–particle interaction. Hence, we simulate the PUI velocity distribution function by solving the PUI transport equations under the assumption that the distribution is isotropic and depends only on the velocity magnitude in the solar wind rest frame. In the PUI transport equations, we include velocity-space advection contributions. We also have additional source terms containing charge exchange. This is the first 3D magnetohydrodynamic model to treat the full kinetic distribution of PUIs. The model, extended with turbulence, is validated against Voyager 2 data. The results are within the range of the observations in the supersonic solar wind.