Finite element approach to global gyrokinetic Particle-In-Cell simulations using magnetic coordinates

We present a fully-global linear gyrokinetic simulation code (GYGLES) aimed at describing the unstable spectrum of the ion-temperature-gradient modes in toroidal geometry. We formulate the Particle-In-Cell method with finite elements defined in magnetic coordinates, which provides excellent numerical convergence properties. The poloidal mode structure corresponding to k(parallel to) = 0 is extracted without approximation from the equations, which reduces drastically the numerical resolution needed. The code can simulate routinely modes with both very long and very short toroidal wavelengths, can treat realistic (MHD) equilibria of any size, and runs on a massively parallel computer. (C) 1998 Elsevier Science B.V.