Collision operator for a strongly magnetized pure electron plasma

Abstract

Collisions are discussed for a pure electron plasma which is so strongly magnetized that the Larmor radius is small compared to the classical distance of closest approach. In this regime, the most important collisions are characterized by an impact parameter which is the order of the distance of closest approach. Assuming that this distance is small compared to the interparticle spacing, a Boltzmann-like collision operator may be derived. In turn, this operator may be reduced to a Fokker–Planck operator, which is integrable. An interesting property of the collision operator results from an adiabatic invariant which is preserved during scattering. There is no energy exchange between the velocity components which are parallel to the field and the velocity components which are perpendicular to the field. This may have implications for a current effort to cool a pure electron plasma to low temperature by cyclotron radiation.