Excitation of electron Bernstein waves by beating of two cosh-Gaussian laser beams in a collisional plasma
Arvind Kumar, Asheel Kumar, Ashish Varma
Abstract
Abstract In this paper, a theoretical study has been proposed for excitation of electron Bernstein waves in collisional plasma with dc magnetic field by nonlinear interactions of two cosh-Gaussian laser beams. The beat wave with frequency <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ω</mml:mi> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mn>1</mml:mn> </mml:msub> </mml:mrow> <mml:mo>−</mml:mo> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> <mml:mo stretchy="false">)</mml:mo> </mml:math> and wave vector <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mi>k</mml:mi> <mml:mo>⃗</mml:mo> </mml:mover> <mml:mo>=</mml:mo> <mml:mrow> <mml:msub> <mml:mover> <mml:mi>k</mml:mi> <mml:mo>⃗</mml:mo> </mml:mover> <mml:mn>1</mml:mn> </mml:msub> </mml:mrow> <mml:mo>+</mml:mo> <mml:mrow> <mml:msub> <mml:mover> <mml:mi>k</mml:mi> <mml:mo>⃗</mml:mo> </mml:mover> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> , exerts a nonlinear ponderomotive force on electrons. This nonlinear force has the potential to drive the electron Bernstein wave in collisional plasma with dc magnetic field. The convective loss of waves in plasma is also discussed. An analytical formalism is developed for power going into the electron Bernstein wave with respect to total laser power. The variation of normalized potential and power distribution profile as a function of beam direction, normalized beat wave frequency, and normalized collisional frequency is demonstrated to excite Electron Bernstein waves (EBWs) under resonance conditions. The spatial shape of laser beam, optimum laser beam width parameter, decentred parameter, extreme value of electron thermal velocity and cyclotron frequency is proposed for much more excitation. This proposed theory of electron Bernstein wave excitation may be applicable for plasma heating.