Shifted metric procedure for flux tube treatments of toroidal geometry: Avoiding grid deformation

Recent treatments of flute-mode-type turbulence in closed magnetic flux sur face geometry align the coordinates to the magnetic field, leaving the fiel d with one nonvanishing contravariant component. Magnetic shear leads to st rong deformation of coordinate cells in the plane perpendicular to the fiel d, impacting the results. To remedy this one can apply shifts in the drift angle coordinate, the one which remains purely periodic. All operations inv olving polarization and nonlinear advection are then performed locally on a n orthogonal grid, allowing arbitrarily sheared and shaped magnetic geometr ies in computations. (C) 2001 American Institute of Physics.