We present a novel code which solves the Vlasov–Fokker–Planck (VFP) equation in three-dimensional magnetic turbulence using finite difference methods. The approach is distinct from particle tracking codes. The angular component of the velocity space distribution function is represented by a spherical harmonic expansion drawing on an approach pioneered by Bell et al (2006 Plasma Phys. Control. Fusion48 R37) for laser–plasma interaction simulations. This method enables the accurate representation of magnetic fields and of the effect of angular scattering effects on a particle distribution function. The code has been verified against both collisional and quasi-linear turbulent transport theories. It is shown to address successfully the physics of cross-field transport in regimes of magnetic field field perturbation amplitude and collisionality that are difficult to study using other approaches.
Quasilinear theory revisited: general kinetic formulation of wave–particle interactions in plasmas