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H. Ji, M. Yamada (Princeton Plasma Physics Lab., Princeton U.)
A small-scale laboratory experiment is proposed to study the fundamental physics of magnetohydrodynamic (MHD) dynamo phenomena in a well-controlled liquid metal torus. Stars (including the sun), many of their planets, and galaxies are known to exhibit self-generation and sustainment of magnetic fields. The explanation of the observed magnetic fields is given by dynamo theories based on an MHD description of the electrically conductive media. Despite varying degrees of success in both theoretical and computational research, the dynamo mechanism remains largely a mystery due to the unavailability of crucial data.
The present proposal calls for a laboratory experiment to study dynamo processes, especially the \alpha-effect (an electromotive force along the mean magnetic field arising from turbulence), in an axisymmetrical geometry in order to provide fundamental data which can be quantitatively compared with leading dynamo theories. Motivated by recent observations of dynamo effects in a toroidal laboratory plasma, an axisymmetrical torus filled with liquid metal is considered, with flows generated by propellers and external magnetic fields applied by coils.
The proposed experiment will address the following important physics issues: (a) how do dynamo effects, especially the \alpha-effect, arise when flow is driven in a conducting fluid with non-vanishing kinetic helicity; (b) how and when do dynamo effects transition from the weak-field limit (kinematic dynamo) to the strong-field limit (self-consistent or MHD dynamo); (c) how do dynamo effects depend on whether a system is driven hydrodynamically or magnetically (such as in laboratory plasma experiments)? (d) how are dynamo effects related to kinetic and magnetic helicity and how does it affect magnetic helicity conservation?
If the author provided an email address or URL for general inquiries, it is a
s follows:
http://w3.pppl.gov/~hji