Full-sphere simulations of a circulation-dominated solar dynamo: Exploring the parity issue

Chatterjee, Piyali; Nandy, Dibyendu; Choudhuri, Arnab Rai

doi:10.1051/0004-6361:20041199

Cited by 225 publications

(359 citation statements)

References 40 publications

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“…For this reason, these models are often referred to as flux-transport (FT) dynamo models. In the literature FT models have been studied extensively by several authors (Dikpati & Charbonneau 1999;Chatterjee et al 2004;Guerrero & Dal Pino 2008, and references therein). These models have now reached a stage where they are able to reproduce the butterfly diagram as well as the correct phase between the polar fields and the toroidal fields.…”

Section: Flux Transport Dynamomentioning

confidence: 99%

Magnetic helicity fluxes in interface and flux transport dynamos

Chatterjee

Gómez

Brandenburg

2010

A&A

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Context. Dynamos in the Sun and other bodies tend to produce magnetic fields that possess magnetic helicity of opposite sign at large and small scales, respectively. The build-up of magnetic helicity at small scales provides an important saturation mechanism. Aims. In order to understand the nature of the solar dynamo we need to understand the details of the saturation mechanism in spherical geometry. In particular, we aim to understand the effects of magnetic helicity fluxes from turbulence and meridional circulation. Methods. We consider a model with only radial shear confined to a thin layer (tachocline) at the bottom of the convection zone. The kinetic α owing to helical turbulence is assumed to be localized in a region above the convection zone. The dynamical quenching formalism is used to describe the build-up of mean magnetic helicity in the model, which results in a magnetic α effect that feeds back on the kinetic α effect. In some cases we compare these results with those obtained from a model with a simple algebraic α quenching formula.Results. In agreement with earlier findings, the magnetic α effect has the opposite sign compared with the kinetic α effect and leads to a catastrophic decrease of the saturation field strength proportional to the inverse magnetic Reynolds number. At high latitudes this quenching effect can lead to secondary dynamo waves that propagate poleward because of the opposite sign of α. These secondary dynamo waves are driven by small-scale magnetic helicity instead of the small-scale kinetic helicity. Magnetic helicity fluxes both from turbulent mixing and from meridional circulation alleviate catastrophic quenching. Interestingly, supercritical diffusive helicity fluxes also give rise to secondary dynamo waves and grand minima-like episodes.

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Section: Flux Transport Dynamomentioning

confidence: 99%

Magnetic helicity fluxes in interface and flux transport dynamos

Chatterjee

Gómez

Brandenburg

2010

A&A

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“…They are Choudhuri et al (2007) and Jiang et al (2007), see also Chatterjee et al (2004). The turbulent diffusivity is in order of 10 12 cm 2 s −1 .…”

Section: Turbulent Diffusivity Dominated Classmentioning

confidence: 94%

Solar-cycle precursors and predictions

Jiang

2012

Proc. IAU

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Abstract. The sunspot number data during the past 400 years indicates that both the profile and the amplitude of the solar cycle have large variations. Some precursors of the solar cycle were identified aiming to predict the solar cycle. The polar field and the geomagnetic index are two precursors which are received the most attention. The geomagnetic variations during the solar minima are potentially caused by the solar polar field by the connection of the solar open flux. The robust prediction skill of the polar field indicates that the memory of the dynamo process is less than 11 yrs based on the frame of the Babcock-Leighton flux transport dynamo. One possible reason to get the short magnetic memory is the high magnetic diffusivity in the convective zone. Our recent studies show that the radial downward pumping is another possible reason. Based upon the mechanism, we well simulate the cycle irregularities during RGO time period. This opens the possibility to set up a standard dynamo based model to predict the solar cycle. In the end, the no correlation between the polar field and the preceding cycle strength due to two nonlinearities involved in the sunspot emergence will be stressed.

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“…They demonstrated how it is possible to tune such models with respect to account of different effects to reproduce particular features of the observable solar magnetic fields and its helical properties. Jiang, Choudhuri and Wang (2007) presented a possibility on the origin of TLs linking with the Babcock Leighton dynamo process based on the model of Chatterjee, Nandy, and Choudhuri (2004). They proposed that TLs are visible signatures of poloidal field lines across the equator.…”

Section: Helicity and Solar Dynamomentioning

confidence: 99%

Helicity of solar magnetic field from observations

Zhang

2009

Proc. IAU

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Abstract. The helicity is an important quantity to present the basic topological configuration of magnetic field transferred form the solar subatmosphere into the interplanetary space. In this paper, we present the observational solar magnetic field and the relationship with the magnetic helicity.Keywords. Sun: magnetic fields, helicity, interior; turbulence, MHD Importance and definition of magnetic helicityHelicities are topologically a measure of the structural complexity of the corresponding fields. Woltjer (1958) presented the basic properties of magnetic helicity firstly. As indicated by Taylor (1986) that the topological invariants of ideal plasma so that only total magnetic helicity survives. Helicity is described in terms of the internal structure of a flux tube and the external relations between flux tubes. The helicity of open field configurations not bounded by magnetic surfaces is discussed by Berger and Field (1984), and a measure of the propagation of topological structures across open boundaries is given also. Pouquet, Frisch, and Leorat (1976) indicated that the turbulence and magnetic fields are a common feature of many celestial bodies. The study confirms the importance of helicity both in its kinetic and in its magnetic form for generation of large-scale magnetic fields by turbulence. Keinigs (1983) and Keinigs and Gerwin (1986) analyzed that in a magnetized plasma the alpha effect represents a turbulently generated emf directed along the mean magnetic field. The alpha effect is reevaluated in terms of ensemble-averaged properties of the magnetic fluctuation spectrum. The results indicate that the turbulent current helicity must be opposite in sign to the mean-field current helicity in order for the alpha effect to play a role in overcoming the resistive diffusion of large-scale magnetic fields. Kleeorin and Rogachevskii (1999) analyzed the evolution of the magnetic helicity tensor for a nonzero mean magnetic field and for large magnetic Reynolds numbers in an anisotropic turbulence.The magnetic helicity density h m =A · B, with A the vector potential for magnetic field B, measures the chirality of magnetic lines of force. The magnetic helicity is defined as

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Full-sphere simulations of a circulation-dominated solar dynamo: Exploring the parity issue

Cited by 225 publications

References 40 publications

Magnetic helicity fluxes in interface and flux transport dynamos

Magnetic helicity fluxes in interface and flux transport dynamos

Solar-cycle precursors and predictions

Helicity of solar magnetic field from observations

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