Resistive MHD mode structures in a tokamak

Thesis/Dissertation · Fri Dec 31 04:00:00 EST 1993

OSTI ID:121160

Che, H Y

Full spectral nonlinear differential equations for a non-uniform, incompressible, resistive, and viscous magnetofluid were established in a periodic cylindrical coordinate system using an expansion in Chandrasekhar-Kendall functions. The system of nonlinear algebraic equations obtained from the nonlinear differential equations in steady-state was solved numerically. Many characteristics of nonlinear resistive MHD phenomena are revealed without introducing the usual boundary layer assumptions on the rational magnetic surfaces by merely solving the nonlinear algebraic equations with given resistivity profiles and current density profiles. Resistive MHD mode structures were determined by the profile properties of the plasma in a tokamak, such as the resistivity profiles, current density profiles, and the nonlinear couplings of one mode to another. The existence of modes prohibited by linear tearing mode theory was predicted by the nonlinear algebraic equations and observed with a set of sinusoidal coil diagnostics in the Phaedrus-T tokamak. The nonlinear algebraic equations suggested that a poloidal rotation as well as toroidal rotation determines mode frequency which is linearly dependent on toroidal mode number. If the poloidal rotation is comparable to the toroidal rotation, the mode frequency is inversely proportional to the poloidal magnetic field rather than toroidal magnetic field in a tokamak. The solutions of the nonlinear algebraic equations agree qualitatively with the mode structures and frequencies measured by the sinusoidal coil diagnostics in the Phaedrus-T tokamak.

• Research Organization: Wisconsin Univ., Madison, WI (United States)
• OSTI ID: 121160
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DIFFERENTIAL EQUATIONS
MAGNETIC SURFACES
MHD EQUILIBRIUM
NONLINEAR PROBLEMS
TOKAMAK DEVICES