Numerical modeling of thermal force in a plasma for test-ion transport simulation based on Monte Carlo Binary Collision Model

We present a new numerical model of the thermal force in a plasma, based on the Monte Carlo Binary Collision Model (BCM) [T. Takizuka, H. Abe, J. Comput.Phys. 25 (1977) 205]. This model can be applied for the transport simulation of test ions. The model consists of two steps: (i) choosing a background plasma ion velocity from a distorted Maxwell distribution under the temperature gradient, and (ii) calculating a Coulomb collision between a test particle and the above chosen ion by using the BCM. For the step (i), we developed a velocity sampling method from a distorted Maxwellian, which enables the BCM to bring the thermal force on a test particle in the step (ii).A systematic series of simulations has been performed under various conditions to examine the model. The results of these simulations have been compared with the theoretical values, and it is shown that our model simulates the thermal force correctly for important characteristic features; dependences on the temperature gradient, the test particle velocity, and the background plasma density.