Control of ordinary and extraordinary waves excitation by an axial magnetic field in motional plasma

Abstract

The propagation of transverse Electromagnetic (EM) waves along a high energy relativistic electron beam passing through a neutralizing heavy ion background is investigated in the presence of an external axial magnetic field. By making use of the linearized fluid equations coupled with Maxwell’s equations the dielectric tensor and the dispersion relation of excited modes are derived. Since the electron motion is considered relativistic and fluid theory of plasma is used to describe the system, the obtained results are applicable to a vast range of high energy density regime. The mutual interaction between EM and Electron Plasma Waves (EPWs) is studied numerically. In the absence of the axial magnetic field, the EPWs and the Extraordinary Electromagnetic (EOEM) waves interact due to the existence of the self-generated magnetic field. The instability caused by this interaction has already been reported [Phys. Plasma.16, 062107 (2009) ]. We found that applying an axial magnetic field will cause deflection to plasma oscillations which enables coupling between EPWs and Ordinary Electromagnetic (OEM) waves as well. The results show that increasing the external magnetic field strength suppresses the growth rate caused by the coupling of EPWs-EOEM and passes it to the growth of EPWs-OEM. Therefore by adjusting the external magnetic field strength, the growth of EOEM and OEM modes can be controlled.