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.
|