The dynamo properties of the reversed field pinch velocity field

Reversed field pinch (RFP) is a toroidal device aiming at magnetic confinement of a plasma in order to reach conditions of thermonuclear reactions. In RFPs, the magnetic and velocity fields self-organize to a saturated state determined by their nonlinear interplay and the values of the transport-coefficients. The question addressed in this article is whether this saturated velocity field is capable of amplifying a seed magnetic field, the so-called dynamo-effect for the astrophysical community. It is shown, using numerical simulations in periodic cylinders, that the RFP velocity field can amplify a passively advected seed-field, but this is only observed for values of the magnetic Prandtl number above unity. These observations are reported for both laminar and turbulent RFP flows. We further assess the difference in behavior between a passively advected vector field and the true magnetic field and show that their difference is associated with the detailed alignment properties of the fields. Published under an exclusive license by AIP Publishing.

Automated summary

This article addresses the question of whether the velocity field in a reversed field pinch (RFP) can amplify a seed magnetic field. Numerical simulations are used to show that the RFP velocity field can indeed amplify a passively advected seed-field, but only when the magnetic Prandtl number is above unity. These observations hold true for both laminar and turbulent RFP flows.