Magnetic flux concentrations from turbulent stratified convection

@article{Kapyla2015MagneticFC,
  title={Magnetic flux concentrations from turbulent stratified convection},
  author={Petri J. Kapyla and Axel Brandenburg and Nathan Kleeorin and M. J. Kapyla and I. Rogachevskii ReSoLVE Center of Excellence and Aalto and University of Helsinki and Nordita and Stockholm University and Jila and Lasp and Ben-Gurion University},
  journal={Astronomy and Astrophysics},
  year={2015},
  volume={588},
  pages={1-13}
}
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References

SHOWING 1-10 OF 68 REFERENCES

Flux concentrations in turbulent convection

Abstract We present preliminary results from high resolution magneto-convection simulations where we find the formation of flux concentrations from an initially uniform magnetic field. The structures

Formation of intense magnetic fields near the surface of the Sun

Convection concentrates magnetic flux into ropes between granules in the solar photosphere, with average fields of up to 1500 G. The magnetic energy density is locally much greater than the kinetic

Properties of the negative effective magnetic pressure instability

As was demonstrated in earlier studies, turbulence can result in a negative contribution to the effective mean magnetic pressure, which, in turn, can cause a large-scale instability. In this study,

Pumping of Magnetic Fields by Turbulent Penetrative Convection

A plausible scenario for solar dynamo action is that the large-scale organized toroidal magnetic field is generated by the action of strong radial shear at the base of the solar convection zone,

Bipolar region formation in stratified two-layer turbulence

This work presents an extensive study of the previously discovered formation of bipolar flux concentrations in a two-layer model. We interpret the formation process in terms of negative effective

Dynamo action in stratified convection with overshoot

Results are presented from direct simulations of turbulent compressible hydromagnetic convection above a stable overshoot layer. Spontaneous dynamo action occurs followed by saturation, with most of

CYCLIC MAGNETIC ACTIVITY DUE TO TURBULENT CONVECTION IN SPHERICAL WEDGE GEOMETRY

We report on simulations of turbulent, rotating, stratified, magnetohydrodynamic convection in spherical wedge geometry. An initially small-scale, random, weak-amplitude magnetic field is amplified

Dynamo action and magnetic buoyancy in convection simulations with vertical shear

A hypothesis for sunspot formation is the buoyant emergence of magnetic flux tubes created by the strong radial shear at the tachocline. In this scenario, the magnetic field has to exceed a threshold

Detection of negative effective magnetic pressure instability in turbulence simulations

We present the first numerical demonstration of the negative effective magnetic pressure instability in direct numerical simulations of stably stratified, externally forced, isothermal hydromagnetic

SIMULATION OF THE FORMATION OF A SOLAR ACTIVE REGION

We present a radiative magnetohydrodynamics simulation of the formation of an active region (AR) on the solar surface. The simulation models the rise of a buoyant magnetic flux bundle from a depth of
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