Magnetic Field Generation in Experiments, Geophysics and Astrophysics
Coordinators: Christopher Andrew Jones, Daniel Perry Lathrop, Steven Michael Tobias, Ellen G. Zweibel
Magnetic fields play a key role in the dynamics of stars, galaxies and planetary interiors. Understanding the origin and nature of these magnetic fields is a major scientific challenge. The conference will bring together leading scientists from a variety of disciplines to advance our knowledge of these problems. Recently, new laboratory experiments have been built to investigate magnetic field generation in fluids. Some have now successfully generated magnetic fields, and others are improving our understanding of nonlinear MHD. Major advances in computing technology and software development have greatly extended the possibilities for numerical simulation of the dynamo process, and theoretical progress has been made in our understanding of fast dynamos and turbulent dynamos.
In this conference, all contributions improving our understanding oe experimental, geophysical and astrophysical dynamos are welcome. Special attention will be given to the following areas.
(i) Nonlinear saturation mechanisms for dynamos.
This is a key issue for stellar and planetary dynamos, and one in which experiments can have a significant impact. The dependence of the magnetic energy and peak field generated on the magnetic and fluid Reynolds numbers, and on the energy input, are currently controversial.
(ii) How experiments and observations constrain dynamo theory.
Many different models of how dynamo action can occur have emerged over the last ten years. Observation and experiment are required to decide which are relevant in astrophysics and geophysics.
(iii) How dynamos can operate at extreme parameter values.
Numerical and laboratory experiments are typically restricted to certain parameter regimes, for example moderate magnetic Reynolds number, and Ekman number, whereas in the objects of interest these numbers are typically very large or very small. Of particular interest currently is the issue of behaviour at small magnetic Prandtl number, that is when the fluid Reynolds number is much larger than the magnetic Reynolds number. The asymptotic behaviour must be evaluated.
(iv) The role of helicity and how energy can cascade from small to large scales, and the effect of anisotropic small scale motion on this process.
Field can be generated at small scales and cascade up to the large observed scales. Helicity and anisotropy can affect how this happens.
(v) Numerical and sub-grid scale modelling in MHD.
New numerical methods are being applied to dynamo theory, some including recently developed LES (large eddy simulation) techniques to model the small scales that cannot be directly computed.