Graduate Student / Postdoc Seminar
Dual Cascades in Gyrokinetic Turbulence
Speaker: Gabriel Plunk, University of Maryland
Location: Warren Weaver Hall 1302
Date: Friday, October 15, 2010, 1:30 p.m.
The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in weakly collisional plasmas, ranging from space settings to fusion devices. In this talk, I'll present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguish this cascade from that of neutral fluid turbulence. These phenomena are explained, in the style of Fjortoft 1953, in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code AstroGK. The basic mechanisms that are revealed in this work provide a framework for understanding interactions in turbulence with coupled dynamics at disparate scales, which is an open and actively researched topic in magnetically confined fusion.