"Generation of shear Alfven waves by high power pulse at the electron plasma frequency"

 

ABSTRACT:

The work I will present focuses on a high power electromagnetic pulse in the electron plasma frequency range impinging on a fully magnetized plasma, at the Large Plasma Device (LAPD) at UCLA. The interaction of the high frequency waves with the plasma leads to the generation of low frequency waves in the shear Alfven wave range. 

 

Waves in the electron plasma frequency range are launched into the radial density gradient, perpendicular to the background magnetic field. The absorption of these waves leads to a pulse of field aligned suprathermal electrons. This electron current pulse then launches an Alfven wave with frequencies below the ion cyclotron frequency. 

 

The experiment was performed both in ordinary mode (O-mode) and extraordinary mode (X-mode), for different background magnetic fields, different temperatures and different power levels of the incoming microwaves.

The Alfven wave generation can be explained by Cherenkov radiation of Alfven waves by the suprathermal electron pulse. Theoretical solutions for the perturbed magnetic field due to a pulse of field aligned electrons were obtained, and shown to be in excellent agreement with the observed Alfven waves.