Quadrupole and octopole electromagnetic waves in slightly non-uniform magnetized plasma column

The paper presents the results of a theoretical study of the dispersion properties, wave field structure and energy characteristics of travelling electromagnetic nonsymmetric surface waves that propagate along a magnetized plasma column surrounded by an infinite vacuum region. The waves with azimuth wave numbers m = +/-2, +/-3 were considered. An external constant magnetic field parallel with respect to the axis of the waveguide system is applied. The theoretical study is carried out using a hydrodynamic model of a cold, radially uniform plasma. The influence of external magnetic field strength and the finite plasma column radius on the dispersion, attenuation and radial wave field structure is studied in the approximation of weak longitudinal plasma density non-uniformity. It is shown, that the external magnetic field essentially affects the dispersion, radial wave field structure and wave damping. Research carried out allows one to estimate the possibility of quadrupole and octopole modes use for gas discharge sustaining. The analysis of the obtained results makes it possible to estimate the plasma density, that can be sustained in gas discharges on quadrupole and octopole waves.