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Résumé |
Primary effect of turbulence is enhancing the effective transports of the system. The representative effects are the eddy viscosity, the anomalous resistivity, the turbulent diffusivity, so on. However, if some symmetry is broken in turbulence, we may have some other effects that suppress the primary effect of turbulence, enhancement of the transport. If turbulence has a finite cross helicity (velocity-magnetic-field correlation) in the presence of the large-scale vortical motion, it induces the electromotive force aligned with the large-scale vorticity. This effect of cross helicity may expand the scope of the dynamo notion in astro- and geophysical phenomena, where large-scale rotational motions are ubiquitously observed. In the talk, the cross helicity effect in dynamo process is discussed with some illustrative examples. Effects of turbulent cross helicity in momentum transport will be also discussed, with special reference to the recent developments in turbulent magnetic reconnection studies. |
