Reply to the Comments of Dikpati et al.

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

doi:10.1051/0004-6361:20052934

Cited by 107 publications

(146 citation statements)

References 9 publications

(26 reference statements)

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“…We show that the physics of what is happening can be understood on the basis of some results presented by Yeates, Nandy and Mackay (2008). It may be mentioned that several authors have recently argued in favour of the high-diffusivity model Jiang, Chatterjee and Choudhuri 2007;Goel and Choudhuri 2009;Choudhuri and Karak 2009;Hotta andYokoyama 2010a, 2010b;Karak 2010;Karak and Choudhuri 2011;Kitchatinov and Olemskoy 2011). The results of this paper provide further support to the high-diffusivity model.…”

Section: Introductionsupporting

confidence: 76%

“…Some of our calculations are done by using exactly same parameters as used by Dikpati and Charbonneau (1999) in their 'reference solution' except for the value of u 0 which is taken as 20 m s −1 rather than 10 m s −1 as quoted by them. Only with this value of u 0 , we are able to reproduce their results .…”

Section: Modelmentioning

confidence: 99%

“…Flux transport dynamo model (Choudhuri, Schüssler, and Dikpati 1995;Durney 1995;Dikpati and Charbonneau 1999;Nandy and Choudhuri 2002;Chatterjee, Nandy, and Choudhuri 2004;Charbonneau 2010; is the most promising model of solar cycle at present. In this model, the strong toroidal field is generated near the base of the convection zone due to the stretching of the poloidal field by the strong differential rotation and the poloidal field is generated near the surface through the Babcock-Leighton mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…The meridional circulation and the turbulent diffusivity are the two important flux transport agents from the source of the poloidal field (near the surface) to the source region of the toroidal field (bottom of the convection zone). The meridional circulation plays a very crucial role in the flux transport dynamo model by determining its period (Dikpati and Charbonneau 1999) and also has an effect on the cycle strength (Yeates, Nandy, and Mackay 2008;Karak 2010). It appears that the meridional circulation is crucial in modeling many irregular features of the solar cycle like the Waldmeier effect (Karak and Choudhuri 2011) and the Maunder-like grand minima (Karak 2010).…”

Section: Introductionmentioning

confidence: 99%

“…During the last few years, two classes of flux transport dynamo models have been developed in considerable details: (i) the high-diffusivity model in which the value of the turbulent diffusivity η in the convection zone is taken in the range ∼ 10 12 -10 13 cm 2 s −1 (Chatterjee, Nandy and Choudhuri 2004; and (ii) the low-diffusivity model in which η in the convection zone is ∼ 10 10 -10 11 cm 2 s −1 (Dikpati and Charbonneau 1999;Dikpati and Gilman 2006). We may note that the simple mixing length theory gives the value of η ∼ 1-4 × 10 12 cm 2 s −1 (Parker 1979, p. 629), similar to what is used in the high-diffusivity model.…”

Section: Introductionmentioning

confidence: 99%

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Quenching of Meridional Circulation in Flux Transport Dynamo Models

Karak

Choudhuri

2012

Sol Phys

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Guided by the recent observational result that the meridional circulation of the Sun becomes weaker at the time of the sunspot maximum, we have included a parametric quenching of the meridional circulation in solar dynamo models such that the meridional circulation becomes weaker when the magnetic field at the base of the convection zone is stronger. We find that a flux transport solar dynamo tends to become unstable on including this quenching of meridional circulation if the diffusivity in the convection zone is less than about 2 × 10 11 cm 2 s −1 . The quenching of α, however, has a stabilizing effect and it is possible to stabilize a dynamo with low diffusivity with sufficiently strong α-quenching. For dynamo models with high diffusivity, the quenching of meridional circulation does not produce a large effect and the dynamo remains stable. We present a solar-like solution from a dynamo model with diffusivity 2.8 × 10 12 cm 2 s −1 in which the quenching of meridional circulation makes the meridional circulation vary periodically with solar cycle as observed and does not have any other significant effect on the dynamo.

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Section: Introductionsupporting

confidence: 76%

Section: Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quenching of Meridional Circulation in Flux Transport Dynamo Models

Karak

Choudhuri

2012

Sol Phys

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Turbulent dynamo near tachocline and reconstruction of azimuthal magnetic field in the solar convection zone

Krivodubskij¹

2005

Astron. Nachr.

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Abstract. In order to extend the abilities of the αΩ dynamo model to explain the observed regularities and anomalies of the solar magnetic activity, the negative buoyancy phenomenon and the magnetic quenching of the α effect were included in the model, as well as newest helioseismically determined inner rotation of the Sun were used. Magnetic buoyancy constrains the magnitude of toroidal field produced by the Ω effect near the bottom of the solar convection zone (SCZ). Therefore, we examined two "antibuoyancy" effects: i) macroscopic turbulent diamagnetism and ii) magnetic advection caused by vertical inhomogeneity of fluid density in the SCZ, which we call the ∇ρ effect. The Sun's rotation substantially modifies the ∇ρ effect. The reconstruction of the toroidal field was examined assuming the balance between mean-field magnetic buoyancy, turbulent diamagnetism and the rotationally modified ∇ρ effect. It is shown that at high latitudes antibuoyancy effects block the magnetic fields in the deep layers of the SCZ, and so the most likely these deep-rooted fields could not become apparent at the surface as sunspots. In the near-equatorial region, however, the upward ∇ρ effect can facilitate magnetic fields of about 3000 -4000 G to emerge through the surface at the sunspot belt. Allowance for the radial inhomogeneity of turbulent velocity in derivations of the helicity parameter resulted in a change of sign of the α effect from positive to negative in the northern hemisphere near the bottom of the SCZ. The change of sign is very important for direction of the Parker's dynamo-waves propagation and for parity of excited magnetic fields. The period of the dynamo-wave calculated with allowance for the magnetic quenching is about seven years, that agrees by order of magnitude with the observed mean duration of the sunspot cycles. Using the modern helioseismology data to define dynamo-parameters, we conclude that north-south asymmetry should exist in the meridional field. At low latitudes in deep layers of the SCZ, the αΩ dynamo excites most efficiency the dipolar mode of the meridional field. Meanwhile, in high-latitude regions a quadrupolar mode dominates in the meridional field. The obtained configuration of the net meridional field is likely to explain the magnetic anomaly of polar fields (the apparent magnetic "monopole") observed near the maxima of solar cycles.

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Differential rotation on the lower main sequence

Küker¹,

Rüdiger

2005

Astron Nachr

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We compute the differential rotation of main sequence stars of the spectral types F, G, K, and M by solving the equation of motion and the equation of convective heat transport in a mean-field formulation. For each spectral type the rotation rate is varied to study the dependence of the surface shear on this parameter. The resulting rotation patterns are all solar-type. The horizontal shear turns out to depend strongly on the effective temperature and only weakly on the rotation rate. The meridional flow depends more strongly on the rotation rate and has different directions in the cases of very slow and very fast rotation, respectively.Comment: 4 pages, 5 figures, Astron. Nachr. 326, 265 (2005

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Reply to the Comments of Dikpati et al.

Abstract: Abstract. We respond to Dikpati et al.'s criticism of our recent solar dynamo model. A different treatment of the magnetic buoyancy is the most probable reason for their different results.

Cited by 107 publications

References 9 publications

Quenching of Meridional Circulation in Flux Transport Dynamo Models

Quenching of Meridional Circulation in Flux Transport Dynamo Models

Turbulent dynamo near tachocline and reconstruction of azimuthal magnetic field in the solar convection zone

Differential rotation on the lower main sequence

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