The Helical MHD Dynamo

Gailitis, A.; Lielausis, O.; Karasev, B.G.; Kirillov, I.R.; Ogorodnikov, A.P.

doi:10.1007/978-94-009-0999-1_50

Cited by 42 publications

(58 citation statements)

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“…Although the experiment was intended to show self-excitation of a magnetic field without any noticeable starting magnetic field, kick-field coils fed by a 3-phase current of variable low frequency were wound around the module in order to measure the sub-critical amplification of the applied magnetic field by the dynamo. This measurement philosophy was quite similar to that of the 1987 experiment [11] and is based on generation theory for prolongated flows as the length of our spiral flow exceeds its diameter more then ten times. Generation in such a geometry should start as exponentially high amplification of some kick-field (known as convective generation) and should transform, at some higher flowrate, into self-excitation without any external kick-field.…”

supporting

confidence: 63%

“…A first liquid metal dynamo experiment quite similar to the present one was undertaken by some of the authors in 1987. Although this experiment had to be stopped (for reasons of mechanical stability) before dynamo action occurred the extrapolation of the amplification factor of an applied magnetic field gave indication for the possibility of magnetic field self-excitation at higher pump rates [5]. Today, there are several groups working on liquid metal dynamo experiments.…”

mentioning

confidence: 99%

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Detection of a Flow Induced Magnetic Field Eigenmode in the Riga Dynamo Facility

et al. 2000

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confidence: 63%

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confidence: 99%

Detection of a Flow Induced Magnetic Field Eigenmode in the Riga Dynamo Facility

et al. 2000

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“…3 As a phenomenon, the dynamo effect has been identified in the RFP plasmas, 4 spheromak plasmas 5 as well as in liquid metals. 6 However, it was not until recently 7 that the direct observation of the dynamo electric field has been attempted by measuring ṽ and B simultaneously, followed by other experiments. [8][9][10] In this paper, we report the results obtained by a series of the detailed experiments 7,11,12 conducted in three RFP devices.…”

Section: ͑1͒mentioning

confidence: 99%

Measurement of the dynamo effect in a plasma

Prager

Almagri

et al. 1996

Physics of Plasmas

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A series of detailed experiments has been conducted in three laboratory plasma devices to measure the dynamo electric field along the equilibrium field line ͑the ␣ effect͒ arising from the correlation between the fluctuating flow velocity and magnetic field. The fluctuating flow velocity is obtained from probe measurement of the fluctuating E؋B drift and electron diamagnetic drift. The three major findings are the following: ͑1͒ The ␣ effect accounts for the dynamo current generation, even in the time dependence through a ''sawtooth'' cycle; ͑2͒ at low collisionality the dynamo is explained primarily by the widely studied pressureless magnetohydrodynamic ͑MHD͒ model, i.e., the fluctuating velocity is dominated by the E؋B drift; ͑3͒ at high collisionality, a new ''diamagnetic dynamo'' is observed, in which the fluctuating velocity is dominated by the electron diamagnetic drift. In addition, direct measurements of the helicity flux indicate that the dynamo activity transports magnetic helicity from one part of the plasma to another, but the total helicity is roughly conserved, verifying Taylor's ͓Phys. Rev. Lett. 33, 1139 ͑1974͒; Rev. Mod. Phys. 58, 741 ͑1986͔͒ conjecture.

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“…denotes complex conjugate. These Ponomarenko dynamos have been discussed as models of magnetic field generation in galactic jets (Shukurov & Sokoloff 1993), and as the basis of a possible experimental realization of a dynamo (Gailitis & Freiberg 1980;Gailitis et al 1987;Gailitis 1993). Numerical simulations of dynamo action in convective flows also show magnetic fields concentrating in swirling downdraughts (e.g.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear equilibration of a dynamo in a smooth helical flow

Bassom

Gilbert

1997

J. Fluid Mech.

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We investigate the nonlinear equilibration of magnetic fields in a smooth helical flow at large Reynolds number Re and magnetic Reynolds number Rm with Re Rm 1. We start with a smooth spiral Couette flow driven by boundary conditions. Such flows act as dynamos, that is are unstable to growing magnetic fields; here we disregard purely hydrodynamic instabilities such as Taylor-Couette modes. The dominant feedback from a magnetic field mode is only on the mean flow and this yields a simplified 'mean-flow system' consisting of one magnetic mode and the mean flow, which we solve numerically. We also obtain the asymptotic structure of the equilibrated fields for weakly and strongly nonlinear regimes. In particular the field tends to concentrate in a cylindrical shell where all stretching and differential rotation is suppressed by the Lorentz force, and the fluid is in solid-body motion. This shell is bounded by thin diffusive layers where the stretching that maintains the field against diffusive decay is dominant.

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The Helical MHD Dynamo

Cited by 42 publications

References 1 publication

Detection of a Flow Induced Magnetic Field Eigenmode in the Riga Dynamo Facility

Detection of a Flow Induced Magnetic Field Eigenmode in the Riga Dynamo Facility

Measurement of the dynamo effect in a plasma

Nonlinear equilibration of a dynamo in a smooth helical flow

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