Refinement of the gyrokinetic equations for edge plasmas with large flow shears

A refined formulation of the gyrokinetic equations for large-flow shears caused by an equilibrium electric field has been presented. It is achieved by choosing more suitable equilibrium drift velocity for the reference frame of a charged particle instead of the previous one [H. Qin, Contrib. Plasma Phys., 46, 477 (2006)]. This modification yields improvements in the accuracy of the gyrokinetic equations even in the case of considerably large flow. The equations of motion and Maxwell's equations are obtained using the Lie perturbation analysis and the pullback technique. From the numerical comparisons of the gyrokinetic equations given by Qin and the one derived here, the advantage of the present formulation is confirmed for both uniform and nonuniform large electric fields. Parameter dependence of the error in the energy expression is also numerically evaluated. (C) 2008 American Institute of Physics.