Excitation of lower hybrid and magneto-sonic perturbations in laser plasma interaction

Abstract

Lower hybrid (LH) and magneto-sonic (MS) waves are well known modes of magnetized plasma. These modes play important roles in many phenomena. The LH wave is often employed in magnetic confinement fusion experiments for current drive and heating purposes. Both LH and MS waves are observed in various astrophysical and space plasma observations. These waves involve ion motion and have not therefore been considered in high power pulsed laser experiments. This paper shows, with the help of particle-in-cell simulations, a simple mechanism for excitation of LH and magnetosonic excitations in the context of laser plasma interaction. A detailed study characterising the formation and propagation of these modes have been provided. The scheme for generating these perturbations relies on the application of a strong magnetic field in the plasma to constrain the motion of lighter electron species in the laser electric field. The magnetic field strength is chosen so as to leave the heavier ions un-magnetized at the laser frequency. This helps in the excitation of the LH waves. At the slower time scale associated with the laser pulse duration, even the ions show a magnetized response and magnetosonic excitations are observed to get excited.