THE RADIAL ELECTRIC-FIELD DYNAMICS IN THE NEOCLASSICAL PLASMAS

A numerical simulation and analytical theory of the radial electric fi eld dynamics in low collisional tokamak plasmas are presented. An init ial value code ''ELECTRIC'' has been developed to solve the ion drift kinetic equation with a full collisional operator in the Hirshman-Sigm ar-Clarke form together with the Maxwell equations. Different scenario s of relaxation of the radial electric field toward the steady-state i n response to sudden and adiabatic changes of the equilibrium temperat ure gradient are presented. It is shown, that while the relaxation is usually accompanied by the geodesic acoustic oscillations, during the adiabatic change these oscillations are suppressed and only the magnet ic pumping remains. Both the collisional damping and the Landau resona nce interaction are shown to be important relaxation mechanisms. Scali ngs of the relaxation rates versus basic plasma parameters are present ed. (C) 1997 American Institute of Physics.