Evolving Submerged Meridional Circulation Cells within the Upper Convection Zone Revealed by Ring‐Diagram Analysis

Haber, D. A.; Hindman, Bradley W.; Toomre, J.; Bogart, R. S.; Larsen, Ryan Godsk; Hill, F.

doi:10.1086/339631

Cited by 315 publications

(341 citation statements)

References 25 publications

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“…The horizontal components of solar subsurface flows are determined over a range of depths from the surface to about 16 Mm using the dense-pack ring-diagram analysis (Haber et al, 2002). Daily flow maps are calculated for 189 dense-pack regions of 15°diameter with centers spaced by 7.5°in latitude and central-meridian distance.…”

Section: Large-scale Flows Around Active Regionsmentioning

confidence: 99%

“…The convergent and divergent flow pattern is one of the most consistent characteristics of subsurface flows associated with active regions. It has been studied with several helioseismic techniques (Gizon, Duvall, and Larsen, 2001;Braun, Birch, and Lindsey, 2004;Haber et al, 2002Haber et al, , 2004Zhao and Kosovichev, 2004;Komm et al, 2005). These extended flows, however, should not be confused with the much more localized moat flow (divergent, 250 m s −1 , see next section and Gizon et al, 2009aGizon et al, , 2009b, which cannot be resolved with 15°-aperture ring analysis.…”

Section: Large-scale Flows Around Active Regionsmentioning

confidence: 99%

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Modeling the Subsurface Structure of Sunspots

et al. 2010

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While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this article, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out a helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by Gizon et al. (2009aGizon et al. ( , 2009b. We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.

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Section: Large-scale Flows Around Active Regionsmentioning

confidence: 99%

Section: Large-scale Flows Around Active Regionsmentioning

confidence: 99%

Modeling the Subsurface Structure of Sunspots

et al. 2010

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“…The ring-diagram method has provided important results about the structure and evolution of large-scale and meridional flows and dynamics of active regions [137,134,138,127,139]. In particular, large-scale patterns of subsurface flows converging around magnetic active regions were discovered [138].…”

Section: Ring-diagram Analysismentioning

confidence: 99%

“…In particular, large-scale patterns of subsurface flows converging around magnetic active regions were discovered [138]. These flows cause variations of the mean meridional circulation with the solar cycle [134], which may affect transport of magnetic flux of decaying active regions from low latitudes to the polar regions, and thus change the duration and magnitude of the solar cycles [140].…”

Section: Ring-diagram Analysismentioning

confidence: 99%

“…Time-distance helioseismology [167] and also local measurements of the pmode frequency shifts by the 'ring-diagram' analysis [134,137,138], have provided synoptic maps of subsurface flows over the whole surface of the Sun. Figure 43 shows a portion of a high-resolution synoptic flow map at the depth of 2 Mm below the surface.…”

Section: Large-scale and Meridional Flowsmentioning

confidence: 99%

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Advances in Global and Local Helioseismology: An Introductory Review

Kosovichev

2011

The Pulsations of the Sun and the Stars

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Abstract. Helioseismology studies the structure and dynamics of the Sun's interior by observing oscillations on the surface. These studies provide information about the physical processes that control the evolution and magnetic activity of the Sun. In recent years, helioseismology has made substantial progress towards the understanding of the physics of solar oscillations and the physical processes inside the Sun, thanks to observational, theoretical and modeling efforts. In addition to the global seismology of the Sun based on measurements of global oscillation modes, a new field of local helioseismology, which studies oscillation travel times and local frequency shifts, has been developed. It is capable of providing 3D images of the subsurface structures and flows. The basic principles, recent advances and perspectives of global and local helioseismology are reviewed in this article.

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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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Evolving Submerged Meridional Circulation Cells within the Upper Convection Zone Revealed by Ring‐Diagram Analysis

Cited by 315 publications

References 25 publications

Modeling the Subsurface Structure of Sunspots

Modeling the Subsurface Structure of Sunspots

Advances in Global and Local Helioseismology: An Introductory Review

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

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