Abstract
Abstract
The outer heliosphere is a dynamic region characterized by the perpetual interaction between the solar wind (SW) and the local interstellar medium (LISM). We model the three-dimensional (3D), time-dependent SW flow throughout the outer heliosphere using the Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), which, in addition to the thermal SW plasma, accounts for charge exchange between the SW ions and interstellar neutral atoms and treats nonthermal ions (i.e., pickup ions, or PUIs) born during this process as a separate fluid. Additionally, MS-FLUKSS allows us to model the transport of turbulence generated by interstellar PUIs in the supersonic SW. We solve the Reynolds-averaged MHD equations using time-varying inner boundary conditions at 1 au that are derived from OMNI data and constrained by Ulysses measurements outside the ecliptic plane. The simulation generally agrees with near-ecliptic measurements of PUIs by Ulysses at 5 au around the Halloween-2003 solar events. The simulation also closely agrees with the SW thermal profile observed by Voyager 2 at 48–78 au well outside the ecliptic plane. Furthermore, the simulation reproduced the large-scale temporal variation of the SW and interstellar PUIs observed by New Horizons (NH) within the ecliptic plane between 11 and 60 au. Comparison of models with or without PUIs and turbulence indicates that PUIs exert profound influence on the dynamic evolution of SW structures in the outer heliosphere. Additionally, the model comparisons suggest that there is significant empirical heating from SW boundary conditions fluctuating on the scale of 1 day, even without PUI-driven turbulence or any SW–LISM interaction at all.