Journal ArticleDOI
Convection in an imposed magnetic field. Part 2. The dynamical regime
TLDR
In this article, the authors investigated two-dimensional magnetoconvection for a fixed Rayleigh number of 104, with the ratio ζ of the magnetic to the thermal diffusivity in the range 0·4 ≥ ζ ≥ 0·05.Abstract:
Nonlinear, two-dimensional magnetoconvection has been investigated numerically for a fixed Rayleigh number of 104, with the ratio ζ of the magnetic to the thermal diffusivity in the range 0·4 ≥ ζ ≥ 0·05. As the Chandrasekhar number Q is decreased, convection first sets in as overstable oscillations, which are succeeded by steady convection with dynamically active flux sheets and, eventually, with kinematically concentrated fields. In the dynamical regime spatially asymmetrical convection, with most of the flux on one side of the cell, is preferred. As Q increases, these asymmetrical solutions become time-dependent, with oscillations about the steady state which develop into large-scale oscillations with reversals of the flow. Although linear theory predicts that narrow cells should be most unstable, the nonlinear results show that steady convection occurs most easily in cells that are roughly twice as wide as they are deep.read more
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Small-scale solar magnetic fields: An overview
TL;DR: An overview of the observational and the theoretical methods used to investigate solar magnetic fields is given in this paper, which includes an introduction to the Stokes parameters, their radiative transfer in the presence of a magnetic field, and empirical techniques used to measure various properties of solar magnetic features.
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Numerical Simulations of Stellar Convective Dynamos. I. The Model and Method
TL;DR: In this paper, a numerical model used to simulate global convection and magnetic field generation in stars is described, where the velocity, magnetic field, and thermodynamic perturbations are expanded in spherical harmonics to resolve their horizontal structure and in Chebyshev polynomials to resolve the radial structure.
Journal ArticleDOI
Nonlinear periodic convection in double-diffusive systems
TL;DR: In this article, the authors studied two examples of two-dimensional nonlinear double-diffusive convection (thermohaline convection and convection in an imposed vertical magnetic field) in the limit where the onset of marginal overstability just precedes the exchange of stabilities.
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Chaos in models of double convection
TL;DR: In this article, a unified approach to derive third-order sets of ordinary differential equations that are asymptotically exact descriptions of weakly nonlinear double convection and that exhibit chaotic behaviour is presented.
References
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Journal ArticleDOI
Small-scale structure of two-dimensional magnetohydrodynamic turbulence
Steven A. Orszag,Cha-Mei Tang +1 more
TL;DR: In this paper, the formation of singularities in two-dimensional magnetohydrodynamic flow is investigated by direct numerical simulation, and it is shown that two dimensional magnetodynamic turbulence is not as singular as three-dimensional hydrodynamic turbulence (in the sense that it has a less highly excited small-scale structure) but that it is more singular than 2D hydrodynamics.
Journal ArticleDOI
Two-dimensional Rayleigh-Benard convection
D. R. Moore,Nigel Weiss +1 more
TL;DR: In this article, the authors studied two-dimensional convection in a Boussinesq fluid confined between free boundaries, with a Prandtl number p = 6·8 and showed that the heat flux is a maximum for square cells; steady convection is impossible for wider cells and finite amplitude oscillations appear instead, with periodic fluctuations of temperature and velocity in the layer.
Journal ArticleDOI
Convection and magnetic fields in stars
D. J. Galloway,N. O. Weiss +1 more
TL;DR: In this article, the authors used numerical experiments on magnetoconvection to discuss the concentration of magnetic flux into isolated ropes in the turbulent convective zones of the Sun or other late-type stars.
Journal ArticleDOI
Nonlinear periodic convection in double-diffusive systems
TL;DR: In this article, the authors studied two examples of two-dimensional nonlinear double-diffusive convection (thermohaline convection and convection in an imposed vertical magnetic field) in the limit where the onset of marginal overstability just precedes the exchange of stabilities.