Showing papers by "Friedrich H. Busse published in 2012"
TL;DR: In this paper, two new experiments on fluid turbulence have attained conditions needed to establish asymptotic scalings for turbulent transports of heat and angular momentum, and the conditions were used to establish conditions needed for turbulent scalings.
Abstract: Two new experiments on fluid turbulence have attained conditions needed to establish asymptotic scalings for turbulent transports of heat and angular momentum.
26 citations
Journal Article•
TL;DR: In this article, two new experiments on fluid turbulence have attained conditions needed to establish asymptotic scalings for turbulent transports of heat and angular momentum, and the conditions were used to establish conditions needed for turbulent scalings.
Abstract: Two new experiments on fluid turbulence have attained conditions needed to establish asymptotic scalings for turbulent transports of heat and angular momentum.
19 citations
TL;DR: A physically consistent model of magnetic field generation by convection in a rotating spherical shell with a minimum of parameters is applied to the Sun in this article, and the model exhibits a number of properties resembling those observed on the Sun.
Abstract: A physically consistent model of magnetic field generation by convection in a rotating spherical shell with a minimum of parameters is applied to the Sun. Despite its unrealistic features the model exhibits a number of properties resembling those observed on the Sun. The model suggests the importance of the non-axisymmetric m = 1 or m = 2 component of the magnetic field for the large-scale solar dynamo.
13 citations
TL;DR: The range of existence and properties of two essentially different chaotic attractors found in a model of nonlinear convection-driven dynamos in rotating spherical shells are investigated in this paper.
Abstract: The range of existence and the properties of two essentially different chaotic attractors found in a model of nonlinear convection-driven dynamos in rotating spherical shells are investigated. A hysteretic transition between these attractors is established as a function of the rotation parameter t. The width of the basins of attraction is also estimated. © 2012 The Royal Swedish Academy of Sciences.
12 citations
TL;DR: In this paper, a 3D numerical study of natural convection in a cubical cavity heated from below and rotating about its vertical axis of symmetry is considered in the case when the two horizontal boundaries are isothermal and the four vertical walls are insulated.
Abstract: A three-dimensional (3D) numerical study of natural convection in a cubical cavity heated from below and rotating about its vertical axis of symmetry is considered in the case when the two horizontal boundaries are isothermal and the four vertical walls are insulated The onset of convection is investigated for moderate values of the Rayleigh number Ra and of the Coriolis parameter τ at three Prandtl numbers, Pr=01,071 and 7 Three stable flow structures have been obtained For small τ the onset of convection corresponds to pattern G1 (with one region each of up- and down-flow), for moderate values to pattern G2 (with two regions each of up- and down-flow) and at elevated Rayleigh numbers the pattern G3 is realized (with three regions each of up- and down-flow) With decreasing Pr the range where the mode G1 is most dangerous is extended The onset of convection always occurs in an oscillatory manner leading to waves propagating in the retrograde direction (with respect to the sense of rotation) along the side walls However, at higher values of Ra transitions to steady regimes of convection occur, at least as long as τ is not too large For smaller Prandtl numbers the steady regimes set in at lower Rayleigh numbers
11 citations
TL;DR: A physically consistent model of magnetic field generation by convection in a rotating spherical shell with a minimum of parameters is applied to the Sun as mentioned in this paper, which exhibits a number of properties resembling those observed on the Sun.
Abstract: A physically consistent model of magnetic field generation by convection in a rotating spherical shell with a minimum of parameters is applied to the Sun. Despite its unrealistic features the model exhibits a number of properties resembling those observed on the Sun. The model suggests that the large scale solar dynamo is dominated by a non-axisymmetric $m=1$ component of the magnetic field.
9 citations
TL;DR: The range of existence and properties of two essentially different chaotic attractors found in a model of nonlinear convection-driven dynamos in rotating spherical shells are investigated in this paper.
Abstract: The range of existence and the properties of two essentially different chaotic attractors found in a model of nonlinear convection-driven dynamos in rotating spherical shells are investigated. A hysteretic transition between these attractors is established as a function of the rotation parameter \ttau. The width of the basins of attraction is also estimated.
9 citations
TL;DR: In this paper, the authors present results on modelling magnetic flux tubes in an unstably stratified medium and the flows around them using 2D axisymmetric magnetohydrodynamic (MHD) simulations.
Abstract: We present results on modelling magnetic flux tubes in an unstably stratified medium and the flows around them using 2D axisymmetric magnetohydrodynamic (MHD) simulations. The study is motivated by the formation of magnetic field concentrations at the solar surface in sunspots and magnetic pores and the large-scale flow patterns associated with them. The simulations provide consistent, self-maintained models of concentrated magnetic field in a convective environment, although they are not fully realistic or directly applicable to the solar case. In this paper, we explore under which conditions the associated flows near the surface are converging (towards the spot centre) or diverging (away from the axis) in nature. It is found that, depending on the parameters of the problem, the results can depend on the initial conditions, in particular for zero or low rotation rates and Prandtl numbers smaller than unity. The solutions with a converging flow generally produce more strongly confined magnetic flux tubes.
5 citations
TL;DR: In this article, a physically motivated change in the boundary condition for the differential rotation was proposed to reverse the propagation of dynamo waves towards higher latitudes, at least at low latitudes.
Abstract: Simple models of magnetic field generation by convection in rotating spherical shells exhibit properties resembling those observed on the sun. The assumption of the Boussinesq approximation made in these models prevents a realistic description of the solar cycle, but through a physically motivated change in the boundary condition for the differential rotation, the propagation of dynamo waves towards higher latitudes can be reversed, at least at low latitudes.
2 citations