Hemispherical dynamos generated by convection in rotating spherical shells

Grote, E.; Busse, F. H.

doi:10.1103/physreve.62.4457

Cited by 52 publications

(46 citation statements)

References 5 publications

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“…Flux patches of both polarities are scattered over the outer boundary. When convection is driven by a buoyancy flux from above rather than from an inner core and the more realistic fixed flux rather than fixed codensity condition is used, a hemispherical dynamo can be found as a third mode (Grote and Busse, 2000;Landeau and Aubert, 2011). It is characterized by strong differences in codensity between the northern and southern hemisphere, strong differential rotation between the hemispheres and concentration of dynamo action and strong magnetic surface flux into one of them.…”

Section: Non-dipolar Solutionsmentioning

confidence: 98%

Iron snow dynamo models for Ganymede

Christensen

2015

Icarus

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Section: Non-dipolar Solutionsmentioning

confidence: 98%

Iron snow dynamo models for Ganymede

Christensen

2015

Icarus

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“…7,8,and 10). We note that hemispherical dynamos, where one of the hemispheres is almost devoid of magnetic fields, have been reported from rapidly rotating spherical shells (Grote & Busse 2000;Busse 2002). These dynamos also exhibit poleward migration of activity belts similar to the results reported here.…”

Section: Dynamo Solutionsmentioning

confidence: 98%

Convective dynamos in spherical wedge geometry

et al. 2009

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Self-consistent convective dynamo simulations in wedge-shaped spherical shells are presented. Differential rotation is generated by the interaction of convection with rotation. Equatorward acceleration and dynamo action are obtained only for sufficiently rapid rotation. The angular velocity tends to be constant along cylinders. Oscillatory large-scale fields are found to migrate in the poleward direction. Comparison with earlier simulations in full spherical shells and Cartesian domains is made.Comment: 9 pages, 10 figures, Astron. Nachr. in press. Version with higher resolution figures is available at http://www.helsinki.fi/~kapyla/publ.htm

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“…3c is also concentrated in the southern hemisphere. However, the hemisphere with the dominant magnetic field can change with time (Grote & Busse 2000). The field also propagates westwards in the rotating frame of reference of the shell.…”

Section: Hydrodynamical Convectionmentioning

confidence: 99%

Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars

Yadav

Gastine

Christensen

et al. 2014

A&A

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Context. Observations of cool stars reveal dark spot-like features on their surfaces. These starspots can be more extended than sunspots and cover a large area of the stellar surface. While sunspots appear only at low latitudes, starspots are also found in polar regions, in particular on rapidly rotating stars. Conventional flux-tube models have been invoked to explain starspot properties. However, these models use several simplifications, and so far, neither sunspots nor starspots have been generated in a self-consistent simulation of stellar magnetic convection. Aims. We aim to clarify the conditions necessary for the spontaneous formation of dark spots in numerical models of convectiondriven stellar dynamos. Methods. We simulated convection and magnetic field generation in rapidly rotating spherical shells assuming anelastic approximation. The high-resolution simulations were performed using a fully spectral magnetohydrodynamic code. Results. We demonstrate for the first time that a self-consistent distributed dynamo can spontaneously generate high-latitude dark spots. Dark spots are generated when a large-scale magnetic field, generated in the bulk of the convection zone, interacts with and locally quenches flow near the surface. Sufficiently strong density stratification and rapid rotation are prerequisites for the formation of sizeable dark spots in the model. Conclusions. Our models present an alternative scenario for starspot formation by distributed dynamo action. Our results also lend strong support to the idea that dynamos in the interiors of rapidly rotating stars might be fundamentally different from the solar one.

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Hemispherical dynamos generated by convection in rotating spherical shells

Cited by 52 publications

References 5 publications

Iron snow dynamo models for Ganymede

Iron snow dynamo models for Ganymede

Convective dynamos in spherical wedge geometry

Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars

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