Collisional parameters of a test particle and a streaming plasma

The collisional interaction of a test-charged particle with a streaming Maxwellian distribution of field particles is considered analytically. Values are found for the collisional parameters of dynamical friction force, diffusion tensor, and rate of energy change for a wide range of field particle densities, temperatures, and streaming velocities. Retention of the velocity dependence of the Coulomb logarithm leads to substantial differences in the values of the parallel component of the diffusion tensor and the rate of energy change for the test particle as compared with the Spitzer values. Collision frequencies for momentum transfer, π/2 angular deflection, and energy change for the test particle and the test plasma are defined, simply related to each other, compared with the Spitzer definitions and evaluated for a simple case. The new definitions for the collision frequencies place in evidence the enhancement of collisional momentum and energy transfer in the absence of stationary thermal equilibrium.