With finite pressure, the saturation of the current-driven tearing mode is obtained in threedimensional nonlinear resistive magnetohydrodynamic simulations for Tokamak plasmas. To effectively focus on the tearing modes, the perturbed pressure effects are excluded while the finite equilibrium pressure effects are retained. With this model, the linear growth rates of the tearing modes are found to be very insensitive to the equilibrium pressure increase. The nonlinear aspects of the tearing modes; however, are found to be very sensitive to the pressure increase in that the saturation level of the nonlinear harmonics of the tearing modes increases monotonically with the pressure rise. The increased level is associated with enhanced tearing island sizes or increased stochastic magnetic field region.

The motion of charged particles in the field of H-waves of a cylindrical and a rectangular waveguide in the presence of a uniform magnetic field is investigated analytically and numerically. We obtain the equations of charged particle motion in the H-wave field under cyclotron resonance conditions, evaluate the width of nonlinear resonances, and establish the criterion for dynamical chaos emergence. The criterion is used to analyse the possibility of stochastic acceleration of charged particles by the field of H-waves of circular and rectangular waveguides in the external magnetic field for x-ray production. The stochastic acceleration of particles in two and three standing waves of a circular resonator and two counter-propagating waves of a rectangular waveguide are investigated. It is shown that, over the course of several hundreds of periods of the microwave field, the kinetic energy of the electrons reaches values of around 1.0 MeV and the average kinetic energy reaches values of the order of 0.3 MeV.