Magnetic dynamo action at low magnetic Prandtl numbers.

  title={Magnetic dynamo action at low magnetic Prandtl numbers.},
  author={Leonid M. Malyshkin and Stanislav Boldyrev},
  journal={Physical review letters},
  volume={105 21},
Amplification of magnetic field due to kinematic turbulent dynamo action is studied in the regime of small magnetic Prandtl numbers. Such a regime is relevant for planets and stars interiors, as well as for liquid-metal laboratory experiments. A comprehensive analysis based on the Kazantsev-Kraichnan model is reported, which establishes the dynamo threshold and the dynamo growth rates for varying kinetic helicity of turbulent fluctuations. It is proposed that in contrast with the case of large… 

Figures and Topics from this paper

Small-scale dynamo at low magnetic Prandtl numbers.
The small-scale dynamo can operate in the regime of low magnetic Prandtl numbers if the magnetic Reynolds number is large enough, and it is concluded that Rm_{crit} provides a stronger constraint in the limit of low Pm than it does for large Pm.
Turbulent magnetohydrodynamic dynamo action in a spherically bounded von Kármán flow at small magnetic Prandtl numbers
Turbulent magnetohydrodynamic (MHD) dynamo action in a spherically bounded electrically conducting flow is investigated numerically. A large-scale two-vortex flow driven by a constant body force is
Turbulent magnetic field amplification from the smallest to the largest magnetic Prandtl numbers
The small-scale dynamo provides a highly efficient mechanism for the conversion of turbulent into magnetic energy. In astrophysical environments, such turbulence often occurs at high Mach numbers,
The small-scale dynamo: breaking universality at high Mach numbers
The small-scale dynamo plays a substantial role in magnetizing the Universe under a large range of conditions, including subsonic turbulence at low Mach numbers, highly supersonic turbulence at high
Traces of large-scale dynamo action in the kinematic stage
Using direct numerical simulations (DNS), we verify that in the kinematic regime, a turbulent helical dynamo grows in such a way that the magnetic energy spectrum remains to high-precision
Hydromagnetic dynamo theory provides the prevailing theoretical description for the origin of magnetic fields in the universe. Here, we consider the problem of kinematic, small-scale dynamo action
Magnetorotational dynamo action in the shearing box
Magnetic dynamo action caused by the magnetorotational instability is studied in the shearing-box approximation with no imposed net magnetic flux. Consistent with recent studies, the dynamo action is
Kinematic dynamo onset and magnetic field saturation in rotating spherical Couette and periodic box simulations
Magnetic fields are ubiquitous in the universe and can be found in celestial bodies, galaxies, stars including our Sun and planets like the Earth or Jupiter. Due to the fact that at least in the
Turbulent magnetic Prandtl number in kinematic magnetohydrodynamic turbulence: two-loop approximation.
The turbulent magnetic Prandtl number in the framework of the kinematic magnetohydrodynamic (MHD) turbulence, where the magnetic field behaves as a passive vector field advected by the stochastic
A Study of the Dynamo Transition in a Self-consistent Nonlinear Dynamo Model
We develop a nonlinear dynamo model that couples the evolution of a large-scale magnetic field with the turbulent dynamics of a magnetofluid system in the small scale by electromotive force. Because


Magnetic Dynamo Action in Helical Turbulence
We investigate magnetic field amplification in a turbulent velocity field with nonzero helicity, in the framework of the kinematic Kazantsev-Kraichnan model. We present the numerical solution of the
Numerical study of dynamo action at low magnetic Prandtl numbers.
The difficulty of resolving a large range of scales is circumvented by combining direct numerical simulations, a Lagrangian-averaged model and large-eddy simulations, and the flow is generated by the Taylor-Green forcing.
Small-scale kinematic dynamo and non-dynamo in inertial-range turbulence.
We investigate the Lagrangian mechanism of the kinematic 'fluctuation' magnetic dynamo in a turbulent plasma flow at small magnetic Prandtl numbers. The combined effect of turbulent advection and
Magnetic-field generation in Kolmogorov turbulence.
It is proposed that the smaller the roughness exponent alpha, the larger the magnetic Reynolds number that is needed to excite magnetic fluctuations and implies that numerical or experimental investigations of magnetohydrodynamic turbulence with small Prandtl numbers need to achieve extremely high resolution in order to describe magnetic phenomena adequately.
We propose a plasma experiment to be used to investigate fundamental properties of astrophysical dynamos. The highly conducting, fast-flowing plasma will allow experimenters to explore systems with
Generation of a magnetic field by dynamo action in a turbulent flow of liquid sodium.
We report the observation of dynamo action in the von Kármán sodium experiment, i.e., the generation of a magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and
Magnetic-field generation in helical turbulence.
It is argued that large- scale and small-scale magnetic fluctuations cannot be effectively separated, and that the conventional model alpha is, in general, not an adequate description of the large-scale dynamo mechanism.
Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers.
Direct numerical simulations of incompressible nonhelical randomly forced MHD turbulence are used to demonstrate for the first time that the fluctuation dynamo exists in the limit of large magnetic
Intermittency and anomalous scaling for magnetic fluctuations
The generation of magnetic fluctuations by turbulent flow of conducting fluid with a zero mean magnetic field for small magnetic Prandtl numbers is studied. The equation for the high-order
Laboratory plasma dynamos, astrophysical dynamos and magnetic helicity evolution
The term ‘dynamo’ means different things to the laboratory fusion plasma and astrophysical plasma communities. To alleviate the resulting confusion and to facilitate interdisciplinary progress, we