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Thursday, Dec. 5, 9:30 am in MTH 3206, University of Maryland, College Park

Nonlinearly sustained turbulence in numerical simulations of magnetized plasma

Prof. Jim Drake

Physics Department University of Maryland, College Park, Maryland

The understanding of many important phenomena in plasma in both space and the laboratory require an understanding of how particles, energy, momentum or current are transported across a magnetic field. Typically classical collisions are too weak to explain the observations and anomalous transport processes must be invoked. The traditional paradigm for "anomalous" transport is that instabilities driven by local inhomogeneities in the system drive plasma flows which nonlinearly develop and then relax the gradients. Work in this area involves extensive computation in 3-D systems as well as analytical analysis of truncated models. A discussion of some of the numerical challenges (and innovative solutions) which arise in studying such problems will be followed by a more detailed discussion of the surprising discovery that the conventional paradigm in some cases fails badly. In systems which are stable to all small amplitude perturbations, fluctuations can self-sustain when excited at finite amplitude as a result of a nonlinear streaming instability which has no counterpart in classical linear instability theory.