Alleviating<i>α</i>quenching by solar wind and meridional flows

Mitra, Dhrubaditya; Moss, D.; Tavakol, Reza; Brandenburg, Axel

doi:10.1051/0004-6361/201015637

Cited by 13 publications

(12 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…( 2) affects properties of the dynamo solutions. This is suggested by results that can be found in the literature (Brandenburg et al 2007;Mitra et al 2010;Guerrero et al 2010;Mitra et al 2011). The physics of helicity loss is poorly understood, and influence the various processes of the helicity flux loss on the properties of magnetic cycles deserves a separate study.…”

Section: Basic Equationsmentioning

confidence: 94%

The Asymmetry of Sunspot Cycles and Waldmeier Relations as a Result of Nonlinear Surface-Shear Shaped Dynamo

Пипин

Kosovichev

2011

ApJ

View full text Add to dashboard Cite

The paper presents a study of a solar dynamo model operating in the bulk of the convection zone with the toroidal magnetic field flux concentrated in the subsurface rotational shear layer. We explore how this type of dynamo may depend on spatial variations of turbulent parameters and on the differential rotation near the surface. The mean-field dynamo model takes into account the evolution of magnetic helicity and describes its nonlinear feedback on the generation of large-scale magnetic field by the α-effect. We compare the magnetic cycle characteristics predicted by the model, including the cycle asymmetry (associated with the growth and decay times) and the duration -amplitude relation (Waldmeier's effects), with the observed sunspot cycle properties. We show that the model qualitatively reproduces the basic properties of the solar cycles.

show abstract

Section: Basic Equationsmentioning

confidence: 94%

The Asymmetry of Sunspot Cycles and Waldmeier Relations as a Result of Nonlinear Surface-Shear Shaped Dynamo

Пипин

Kosovichev

2011

ApJ

View full text Add to dashboard Cite

show abstract

“…In the context of the galactic dynamo, alleviation of catastrophic quenching thanks to a wind has been studied in mean-field models by Shukurov et al (2006) and Sur et al (2007). Mitra et al (2011) studied the role of a wind in solar mean-field dynamo models. The models studied in the present paper allow us to compare with their results and to determine the importance of magnetic helicity fluxes in the dynamical evolution of the magnetic α-effect.…”

Section: Introductionmentioning

confidence: 99%

Turbulent dynamos with advective magnetic helicity flux

Sordo¹,

Gómez²,

Brandenburg³

2012

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

Many astrophysical bodies harbor magnetic fields that are thought to be sustained by a dynamo process. However, it has been argued that the production of large-scale magnetic fields by mean-field dynamo action is strongly suppressed at large magnetic Reynolds numbers owing to the conservation of magnetic helicity. This phenomenon is known as catastrophic quenching. Advection of magnetic fields by stellar and galactic winds toward the outer boundaries and away from the dynamo is expected to alleviate such quenching. Here we explore the relative roles played by advective and turbulentdiffusive fluxes of magnetic helicity in the dynamo. In particular, we study how the dynamo is affected by advection. We do this by performing direct numerical simulations of a turbulent dynamo of α 2 type driven by forced turbulence in a Cartesian domain in the presence of a flow away from the equator where helicity changes sign.Our results indicate that in the presence of advection, the dynamo, otherwise stationary, becomes oscillatory. We confirm an earlier result for turbulent-diffusive magnetic helicity fluxes that for small magnetic Reynolds numbers (Rm 100...200, based on the wavenumber of the energy-carrying eddies) the magnetic helicity flux scales less strongly with magnetic Reynolds number (Rm −1/2 ) than the term describing magnetic helicity destruction by resistivity (Rm −1 ). Our new results now suggest that for larger Rm the former becomes approximately independent of Rm, while the latter falls off more slowly. We show for the first time that both for weak and stronger winds, the magnetic helicity flux term becomes comparable to the resistive term for Rm 1000, which is necessary for alleviating catastrophic quenching.

show abstract

“…A relevant quantification of this effect involves considerations of magnetic helicity evolution(e.g., Kleeorin et al, 1995;2003). Again, this scenario is not the only one that has been suggested: for example Brandenburg (2007) considers coronal-mass ejections as an important part of nonlinear suppression of the dynamo, and Mitra et al (2011) consider the effects of the solar wind.…”

Section: Introductionmentioning

confidence: 99%

Current helicity constraints in solar dynamo models

et al. 2012

Self Cite

View full text Add to dashboard Cite

Abstract.We investigate to what extent the current helicity distribution observed in solar active regions is compatible with solar dynamo models. We use an advanced 2D mean-field dynamo model with dynamo action largely concentrated near the bottom of the convective zone, and dynamo saturation based on the evolution of the magnetic helicity and algebraic quenching. For comparison, we also studied a more basic 2D mean-field dynamo model with simple algebraic alpha quenching only. Using these numerical models we obtain butterfly diagrams for both the small-scale current helicity and the large-scale magnetic helicity, and compare them with the butterfly diagram for the current helicity in active regions obtained from observations. This comparison shows that the current helicity of active regions, as estimated by −A · B evaluated at the depth from which the active region arises, resembles the observational data much better than the small-scale current helicity calculated directly from the helicity evolution equation. Here B and A are respectively the dynamo generated mean magnetic field and its vector potential.

show abstract

Alleviatingαquenching by solar wind and meridional flows

Cited by 13 publications

References 26 publications

The Asymmetry of Sunspot Cycles and Waldmeier Relations as a Result of Nonlinear Surface-Shear Shaped Dynamo

The Asymmetry of Sunspot Cycles and Waldmeier Relations as a Result of Nonlinear Surface-Shear Shaped Dynamo

Turbulent dynamos with advective magnetic helicity flux

Current helicity constraints in solar dynamo models

Contact Info

Product

Resources

About