MAGNETIC-FIELD DIFFUSION IN SEMI-IDEAL MAGNETOHYDRODYNAMICS

Diffusion of magnetic fields in semi-ideal magnetohydrodynamics (sigma (parallel to)=infinity sigma(perpendicular to) is finite) is studied. Though the magnetic field is frozen into an auxiliary medium, current layers are shown to develop for generic initial conditions. The final stage of the magnetic field evolution is described by a two-dimensiona l isotopological diffusion equation for the magnetic streamfunction ps i(x,y): partial derivative(t) psi={psi,chi}, where chi is the streamfu nction of the auxiliary medium given by del(chi)(2)={psi del(2) psi}, and {,} is a two-dimensional Jacobian. (C) 1995 American Institute of Physics.