Fast Magnetoacoustic Waves Research Articles

Oblique Nonlinear Hydromagnetic Waves in a Collision-Free Plasma with Isothermal Electron Pressure

Hydromagnetic waves of small but finite amplitude propagating at an arbitrary angle to a magnetic field in a collision-free plasma with isothermal electron pressure are investigated on the basis of a nonlinear perturbation method. It is shown that in the lowest order of perturbation the system of the basic equations can be reduced to two types of the Korteweg-de Vries equations which describe the fast and slow magneto-acoustic waves. Another nonlinear dispersive equation can be obtained for the Alfven wave. The effect of the isothermal electron pressure on the structure of the waves is discussed in detail. Necessary conditions for the existence of the solitary waves in the plasma under consideration are also given.

Cerenkov absorption of Alfvén waves and of fast magneto-acoustic waves in an inhomogeneous plasma

We investigate Cerenkov electron absorption of low-frequency electromagnetic waves in an inhomogeneous plasma cylinder. Formulas were obtained for the energy absorbed by plasma, and for the damping factor where there is no resonance layer. A sharp boundary leads to a strong absorption increase. For a resonance layer containing a point at which the radial wave number becomes infinite, there occurs a strong absorption increase (if the phase velocity of the wave is the order of thermal-electron velocity, then the damping rate is the same order as the frequency). The radial and axial components of the electric field of the wave then increase sharply in the resonance layer. The increase in absorption is caused by the axial component of the electric field. Formulas were derived for the electric field strength inside the resonance layer, for the high-frequency power that is absorbed by the layer; and for the width of the layer.