Ion thruster plumes, consisting of neutrals, ions, and electrons, interact with the spacecraft surface and the solar panels in the backflow region, affecting their performance 1. Therefore, an understanding of the plume characteristics, the charge-exchange reactions2, and ion energy distribution in the backflow region plays an important role in the design of such thrusters. Generally, ion thruster plumes are modeled using a single-temperature Boltzmann relation to obtain the electric potential under the assumption of quasi-neutrality. However, the electron temperature not only varies as a result of expansion, but is also found to be anisotropic. Recently, we developed a three-dimensional, multi-GPU, octree-based PIC-DSMC3 solver to self-consistently model the induced electric field as well as the momentum and charge-exchange reactions.