3D Finite Larmor Radius Guiding Center Model of a Plasma Edge

The turbulent evolution of a 3D guiding center plasma at the plasma edge was simulated using a parallel computer. The plasma edge is represented by a three dimensional Cartesian plasma layer, where the x direction corresponds to the poloidal periodic direction, the y direction to the radial non-periodic direction and the z direction to the toroidal periodic direction. The magnetic, field is regarded as constant, and is situated in the xz-plane making an angle 89.5grd with the x-axis. The model comprises two particle species, electrons and ions with mi/me=1840. The electrons are described by their distribution function fe, whereas the ions are given by their number density ni. The temporal evolution of fe, and ni is determined by the gyrokinetic equation and the gyrofluid continuity equation, respectively. The movement of the ions parallel to the magnetic field is neglected. Due to the spatial dimensions of the plasma layer finite Larmor radius effects must be incorporated into the model. A finite Larmor radius correction procedure [1] is applied, which leads to a charge separation at the plasma edge. This charge separation is accentuated by the polarization drift, which is also comprised in the model in addition to the -drift. Similar models with two spatial dimensions were studied before [2] and showed that for an angle theta close to 90 degrees, the energy tends to condense in the low Fourier modes, reproducing one of the characteristics of the so called inverse cascades. Preliminary results have been published in Ref.[3]. The inclusion of the z (toroidal) direction became possible by using a parallel computer. The temporal evolution and the saturation level of the modes of the electric potential in z direction is studied for several extensions Lz of the plasma layer and compared with the predictions of linear theory.