LAUSR

The Fokker-Planck equation describing the diffusion of energetic particles interacting with turbulence is difficult to solve analytically. Numerical solutions are of course possible but they are not useful for applications. In the past a subspace approximation was proposed which allows to compute important quantities such as the characteristic function as well as certain expectation values. This previous approach was applied to solve the one-dimensional Fokker-Planck equation which contains only a pitch-angle scattering term. In the current paper we extend this approach in order to solve the Fokker-Planck equation for the three-dimensional case including a perpendicular diffusion term. Several expectation values are computed based on our new solution.