Plasmon instability under four external fields

The plasmon instability in a laboratory produced plasma in the presence of four external fields, namely two laser fields, one strong magnetic field an d one static electric field, is discussed. The method of unitary transforma tions is used to transform the problem of electron motion under the four ex ternal fields to that of an electron in the presence only of crossed electr ic and magnetic fields. A kinetic equation for the plasmon population is de rived from which the damping (amplification) rate is calculated. We found t hat the joint action of the four fields results in a relatively larger ampl ification rate fur some values of the static electric field in contrast to the case where no electric field is present. It was also found that the pla smon growth rate factors plasmon wave vectors in an extremely narrow band i .e., the plasmon instability in four external fields is a very selective me chanism for plasmon excitation.