Collisional delta-f scheme with evolving background for transport time scale simulations

The δf approach is extended for simulating the transport time-scale evolution of near-Maxwellian distributions in collisional plasmas. This involves simultaneously advancing weighted marker particles for representing the intrinsically kinetic component δf, and fluid equations for the parameters of the shifted Maxwellian background fSM. The issue of increasing numerical noise in a collisional δf algorithm, due to marker particle weight spreading, is addressed in detail, and a solution to this problem is proposed. To obtain higher resolution in critical regions of phase space, a practical procedure for implementing sources and sinks of marker particles is developed. As a proof of principal, this set of methods is applied for computing electrical Spitzer conductivity as well as collisional absorption in a homogeneous plasma.