Plasma Physics Seminar
Monday, November 26
1310 Sterling Hall
Speaker: Professor Fred Skiff, University of Iowa
"Observing the Acceleration of Suprathermal Electrons by Alfven Waves using the Diagnostic of Whistler-Mode Wave Absorption"
Abstract: Shear Alfven waves are believed to accelerate plasma electrons through both linear and nonlinear wave-particle interactions. In the LAPD plasma device wave packets of nearly-periodic plane waves with dB/B~10E-5 are generated using an arbitrary spatial waveform antenna in the central region of the plasma. When the perpendicular wavelength is shortened to a few times the collisionless skin depth a parallel electric field is produced that should be able to accelerate plasma electrons. The difficulty in observing these electrons is that the change to the distribution function is small and should be greatest at high velocity where the total number of particles is small. Preliminary results of using whistler-mode wave absorption as a diagnostic of the suprathermal electrons indicate that it is indeed possible to observe the effects produced by electron acceleration. We will discuss the problems of separating out the effect of changes in the bulk plasma density (including ducting) from the effects of wave damping (of the whistler-mode wave) that enable us to measure the perturbed electron velocity distribution to high resolution.