Observationally Guided Models for the Solar Dynamo and the Role of the Surface Field

Cameron, Robert H.; Schüssler, Manfred

doi:10.1007/s11214-023-01004-7

Cited by 15 publications

(11 citation statements)

References 193 publications

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“…Following the arguments of CS15, it is tempting to conclude that the poloidal magnetic flux produced by the magnetic flux of bipolar magnetic regions (BMRs) is sufficient for maintaining the solar dynamo. Indeed, this idea has been implemented in the Babcock-Leighton flux transport dynamo models (Babcock 1961;Leighton 1969;Cameron & Schüssler 2023;Hazra et al 2023). It is worth noting that the arguments of CS15 are based on the assumption that the contribution of the line integral along the equator in the convection zone is negligible compared to the contribution of the surface integral in the equation for the total toroidal flux rate formula derived by applying Stokes's theorem.…”

Section: Introductionmentioning

confidence: 99%

Toroidal Magnetic Flux Budget in Mean-field Dynamo Model of Solar Cycles 23 and 24

Pipin,

Kosovichev

2024

ApJ

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We study the toroidal magnetic flux budget of the axisymmetric part of a data-driven 3D mean-field dynamo model of Solar Cycles 23 and 24. The model simulates the global solar dynamo that includes the effects of the formation and evolution of bipolar magnetic regions (BMRs) emerging on the solar surface. By applying Stokes’s theorem to the dynamo induction equation, we show that the hemispheric magnitude of the net axisymmetric toroidal magnetic field generation rate in the bulk of the convection zone can only partially be estimated from the surface parameters of the differential rotation and the axisymmetric radial magnetic field. The contribution of the radial integral along the equator, which is mostly due to the rotational radial shear at the bottom of the convection zone, has the same magnitude and is nearly in phase with the effect of the surface latitudinal differential rotation. Also, the toroidal field generation rate estimate strongly depends on the latitudinal profile of the surface radial magnetic field near the poles. This profile in our dynamo models significantly deviates from the polar magnetic field distribution observed during the minima of Solar Cycles 22, 23, and 24. The cause of this discrepancy requires further observational and theoretical studies. Comparing the 2D axisymmetric and the 3D nonaxisymmetric dynamo models, we find an increase in the toroidal field generation rate in the 3D model due to the surface effects of BMRs, resulting in an increase in the axisymmetric poloidal magnetic field magnitude.

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Section: Introductionmentioning

confidence: 99%

Toroidal Magnetic Flux Budget in Mean-field Dynamo Model of Solar Cycles 23 and 24

Pipin,

Kosovichev

2024

ApJ

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“…ARs are regarded as combinations of dynamical flux systems (Jiang 2020;Zhang & Jiang 2022;Cameron & Schüssler 2023;Jiang et al 2023). Their evolution processes generally include a developing phase and a decaying phase.…”

Section: Active Region Evolution Phasesmentioning

confidence: 99%

Light Bridges and Solar Active Region Evolution Processes

Li,

Rao,

Zhao

et al. 2024

ApJS

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The formation mechanism of light bridges (LBs) is strongly related to the dynamic evolution of solar active regions (ARs). To study the relationship between LB formation and AR evolution phases, we employ 109 LB samples from 69 ARs in 2014 using observational data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. LBs are well matched with the weak field lanes (WFLs), except those aligned on the polarity inversion line of δ sunspots. For penumbral intrusion (type-A) and umbral-dot emergence (type-C) LBs, the WFLs represent the splitting of magnetic flux systems. The sunspots tend to decay and split into several parts after type-A and type-C LBs are formed. For sunspot/umbra-merging (type-B) LBs, the declining WFLs are caused by collisions of flux systems. The sunspots merged and remained stable after type-B LBs formed. We conclude that type-B LBs are formed by collisions of flux systems, while type-A and type-C LBs are generated by splits. The time differences (δ T) between LBs appearing and ARs peaking have an average value of 1.06, −1.60, and 1.82 days for type-A, B, and C LBs, with the standard deviations of 3.27, 2.17, and 1.89, respectively. A positive value of δ T means that the LB appears after the AR peaks, whereas a negative δ T means it appears before the peak. Type-A LBs tend to form in the decaying phase or around the peak time. Type-B LBs are more likely to be formed in the developing phase. Type-C LBs mostly take shape in the decaying phase of ARs.

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“…Thus, the dynamo problem consists of producing a flow field v that has inductive properties capable of sustaining B against turbulent diffusion. The toroidal magnetic field is generated from differential rotation operating on a preexisting poloidal component, and in flux-transport dynamos, the poloidal field is generated from a preexisting toroidal component that emerges through the solar surface (see Charbonneau (2020); Cameron and Schüssler (2023) and references therein).…”

Section: The Stable Solar Dynamo Model -Kinematic Inductionmentioning

confidence: 99%

Inflows towards Bipolar Magnetic Active Regions and Their Nonlinear Impact on a Three-Dimensional Babcock-Leighton Solar Dynamo Model

Teweldebirhan,

Miesch,

Gibson

2023

Preprint

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The changing magnetic fields of the Sun are generated and maintained by a solar dynamo, the exact nature of which remains an unsolved fundamental problem in solar physics. Our objective in this paper is to investigate the role and impact of converging flows toward Bipolar Magnetic Regions (BMR inflows) on the Sun's global solar dynamo. These flows are large-scale physical phenomena that have been observed and so should be included in any comprehensive solar dynamo model. We have augmented the Surface ﬂux Transport And Babcock–LEighton (STABLE) dynamo model to study the nonlinear feedback effect of BMR inflows with magnitudes varying with surface magnetic fields. This fully-3D realistic dynamo model produces the sunspot butterfly diagram and allows a study of the relative roles of dynamo saturation mechanisms such as tilt-angle quenching and BMR inflows. The results of our STABLE simulations show that BMR inflows significantly affect the evolution of the BMRs themselves and result in a reduced buildup of the global poloidal field due to local flux cancellation within the BMRs, to an extent that is sufficient to saturate the dynamo. As a consequence, for the first time, we have achieved fully 3D solar dynamo solutions in which BMR inflows alone regulate the amplitudes and periods of the magnetic cycles.

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Observationally Guided Models for the Solar Dynamo and the Role of the Surface Field

Cited by 15 publications

References 193 publications

Toroidal Magnetic Flux Budget in Mean-field Dynamo Model of Solar Cycles 23 and 24

Toroidal Magnetic Flux Budget in Mean-field Dynamo Model of Solar Cycles 23 and 24

Light Bridges and Solar Active Region Evolution Processes

Inflows towards Bipolar Magnetic Active Regions and Their Nonlinear Impact on a Three-Dimensional Babcock-Leighton Solar Dynamo Model

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