Bill Dorland In classical plasma physics, the Fokker-Planck equation describes the evolution of the one-particle probability density function in six dimensions -- three spatial dimensions and three velocity-space dimensions. When collisional interactions are relatively frequent, the velocity-space information collapses to the minimum required for consistency with conservation of particles, momentum and energy. Collisions rapidly destroy any structures in the velocity space more sophisticated than a Maxwellian. What remains to be understood is therefore a set of fluid conservation laws, set in ordinary three-dimensional space. When one takes into account the electromagnetic interactions, Maxwell's equations must also be solved. Plasma (and neutral fluid) turbulence in this collisional limit has been successfully studied for decades. However, in many key areas of plasma physics (including magnetic con?nement fusion experiments, the solar wind, astrophysical accretion ?ows, collisionless shocks, and magnetic reconnection) collisions are relatively infrequent, and one is faced with the considerably more challenging problem of understanding turbulent, multiscale dynamics evolving in more than three dimensions. I will describe recent progress in identifying and quantifying fundamental features of a large and important subset of such systems. Theoretical, numerical and observational results will be presented.
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