Title: Turbulence in solar wind and astrophysical plasmas
Astronomy Spring Colloquia March 27, 2012 Tuesday, 4:30pm-5:30pm, Peyton Hall auditorium:
Turbulence is complex nonlinear dynamical behavior of a fluid system, whether it be hydrodynamic, magnetohydrodynamic or plasma. These models describe the solar wind, solar corona, planetary magnetospheres, interstellar medium, ionosphere, and related flows in many astrophysical venues. Turbulence involves interaction of many degrees of freedom and broadband couplings across wide ranges of space and time scales. The phenomenon is partially described by wavenumber and frequency spectra, which make it possible to distinguish between waves and turbulence, and to understand the anisotropy of fluctuations. However this description cannot be complete. Nonlinear interactions cause self-organization through relaxation processes, and from this emerges coherent structure, non-Gaussian distributions and intermittency, which can be revealed using conditional statistics. Examples are channeling or dropouts of energetic particles, and nonuniform, patchy heating. These theoretical aspects of dynamical turbulence will be illustrated using numerical simulations, and observed properties of the solar corona, solar energetic particles, solar wind observations and laboratory experimental data.