Magnetohydrodynamic experiments on cosmic magnetic fields

Abstract

It is widely known that cosmic magnetic fields, i.e. the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields play also an active role in cosmic structure formation by enabling outward transport of angular momentum in accretion disks via the magnetorotational instability (MRI). Considerable theoretical and computational progress has been made in understanding both processes. In addition to this, the last ten years have seen tremendous efforts in studying both effects in liquid metal experiments. In 1999, magnetic field self-excitation was observed in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment. An MRI-like mode was found on the background of a turbulent spherical Couette flow at the University of Maryland. Evidence for MRI as the first instability of an hydrodynamically stable flow was obtained in the "Potsdam Rossendorf Magnetic Instability Experiment" (PROMISE). In this review, the history of dynamo and MRI related experiments is delineated, and some directions of future work are discussed.

25 pages, 26 figures, to appear in ZAMM

References in corpus (16)

• Experimental observation and characterization of the magnetorotational instability
• Scale dependence of alpha effect and turbulent diffusivity
• A self-sustaining nonlinear dynamo process in Keplerian shear flows
• Experiments on the magnetorotational instability in helical magnetic fields
• History and results of the Riga dynamo experiments
• Destabilisation of hydrodynamically stable rotation laws by azimuthal magnetic fields
• Why dynamos are prone to reversals
• Traveling waves in magnetized Taylor-Couette flow
• Magnetorotational-type instability in Couette-Taylor flow of a viscoelastic polymer liquid
• Reversals in nature and the nature of reversals
• Reduction of boundary effects in spiral MRI experiment PROMISE
• Nonlinear simulations of magnetic Taylor-Couette flow with current-free helical magnetic fields
• Cylindrical anisotropic ${\alpha }^2$ dynamos
• Coexisting stochastic and coherence resonance in a mean-field dynamo model for Earth's magnetic field reversals
• Magnetic induction in a turbulent flow of liquid sodium: mean behaviour and slow fluctuations
• Magnetorotational instability in electrically driven fluids

Cited by in corpus (3)

• Determining role of Krein signature for 3D Arnold tongues of oscillatory dynamos
• Inferring basic parameters of the geodynamo from sequences of polarity reversals
• Liquid metal experiments on the helical magnetorotational instability