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Dates: June 27 to 30 2006

Venue:

Coordinators:

• David Montgomery (Dartmouth College)
• Annick Pouquet (NCAR/GTP)
• Paul Roberts (Unverstiy of California at Los Angeles)

The National Center for Atmospheric Research will host a workshop in Boulder, Colorado, June 27-30, 2006 sponsored by the Geophysical Turbulence Program (GTP) of the Institute for Mathematics Applied to Geosciences (IMAGe). The workshop will bring together researchers using different approaches to the understanding of MHD turbulence in general and to the generation of magnetic fields (the dynamo process) with particular emphasis on the geo-dynamo and other flows at low magnetic Prandtl number. The approaches considered are modeling, experiments, theory and direct numerical simulations.

Scientific Program:

One of the most persistent difficulties in the computation of the turbulent behavior of fluids and magnetofluids is the wide range of dynamically interacting length and time scales that may have to be evaluated. At large Reynolds number, many orders of magnitude in length scales are implied. Indeed, we observe a great variety of scales in the dynamical behavior of the atmosphere and oceans, in hurricane dynamics, in the solar wind, and the Sun, to cite some familiar examples.

For many purposes, it might be adequate to compute only the long-wavelength components of the spectra of the fields involved if some more economical representation or model of the small-scale behavior could be provided which would not adversely affect the accuracy with which the large scales are computed. Such topics as "large eddy simulation" and "eddy viscosity," designed to cope with this difficulty, have generated a vast literature, but there is also the more difficult problem of obtaining a clear physical understanding of the nature of these approximations as well as extending them to more complex fluids than the ones they were first derived for in the context of fluid dynamics.

Moreover, the generation of the magnetic fields observed in many celestial bodies often occurs in media for which the viscosity ν and the magnetic diffusivity η are vastly different. For example, in the interstellar medium, the magnetic Prandtl number P_M = ν/η can be as large as 10¹⁴, whereas in stars such as the Sun and for planets such as Earth, it can be very low (lower than 10^-5, the value for the Earth fluid core); similarly, in liquid breeder reactors and in laboratory experiments with liquid metals, we have P_M << 1. Mores scales must therefore be resolved, suggesting that more regimes at different scales may arise.

Workshop Format:

The workshop will be organized mainly around invited talks and discussions, in which the speakers will discuss the various approaches to these topics. Sessions are planned on modeling turbulent flows and theoretical, experimental and numerical issues in MHD turbulence and dynamos, with a special emphasis on the geo-dynamo. Contributions may also be made by participants in poster form, or time permitting an oral presentation (see Abstract Submission for more information).

To register for the workshop, please visit the Registration web page.

Invited Speakers:

Tentative Speakers:

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