A 3D Global Simulation of the Heliosphere with Hot Electrons

Currently, global models of the heliosphere are unable to match the positions of the termination shock and heliopause, as well as the plasma conditions observed by Voyager (Provornikova et al. 2014; Michael et al. 2015; Opher et al. 2020; Izmodenov and Alexashov 2020). The current models do not treat electrons separately and assume that they are cold (same temperature as the thermal solar wind). Chalov & Fahr (2013); Fahr et al. 2015 argue for hot electrons (same temperature as pick up ions) downstream of the termination shock. Additionally, Zieger et al. (2015) showed that to accurately match the plasma conditions of Voyager 2's third crossing of the termination shock using MHD models, a population of hot electrons must be included. These hot electrons are energetic enough that electron impact ionization becomes important (Gruntman 2015), which can lead to significant mass loading of the plasma in the heliosheath. Hot electrons were not observed by Voyager 2 (Richardson et al. 2008), but Fahr et al. (2015) argue that a strong negative potential on the surface of the spacecraft would have prevented it from detecting any hot electrons with energy below 30 eV. We extend the multi-ion MHD model of Opher et al. (2020) to include a separate electron fluid in addition to a thermal solar wind and pick-up ion fluid. We Investigate the effect of a hot or cold electron population on the heliosphere. We present a comparison of global multi-ion MHD simulations of the heliosphere with a cold and a hot electron component. We discuss implications for the heliospheric boundaries, and properties of the heliosheath. We discuss future steps such as including the solar cycle time dependence of solar wind. This project is part of the SHIELD NASA DRIVE Science Center.