Surface flux transport simulations: Effect of inflows toward active regions and random velocities on the evolution of the Sun’s large-scale magnetic field

Martin-Belda, David; Cameron, R. H.

doi:10.1051/0004-6361/201527213

Cited by 22 publications

(21 citation statements)

References 26 publications

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“…For all the values of the FWHM, the average amplitude of the axial dipole moment decreases relative to their no-inflows counterpart. This is due to the quenching of the contribution of the BMRs to the global dipole induced by the inflows, which is determined by the magnetic flux of the BMR and the latitudinal separation of the polarities (Martin-Belda & Cameron 2016). The inflows act to enhance the cancellation of opposite polarity flux and limit the latitudinal separation of the polarities, resulting in a reduction of such contribution.…”

Section: Inflow Parametersmentioning

confidence: 99%

Inflows towards active regions and the modulation of the solar cycle: A parameter study

Martin-Belda

Cameron

2016

A&A

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Aims. We aim to investigate how converging flows towards active regions affect the surface transport of magnetic flux, as well as their impact on the generation of the Sun's poloidal field. The inflows constitute a potential non-linear mechanism for the saturation of the global dynamo and may contribute to the modulation of the solar cycle in the Babcock-Leighton framework. Methods. We build a surface flux transport code incorporating a parametrized model of the inflows and run simulations spanning several cycles. We carry out a parameter study to assess how the strength and extension of the inflows affect the build-up of the global dipole field. We also perform simulations with different levels of activity to investigate the potential role of the inflows in the saturation of the global dynamo.Results. We find that the interaction of neighbouring active regions can lead to the occasional formation of single-polarity magnetic flux clumps inconsistent with observations. We propose the darkening caused by pores in areas of high magnetic field strength as a plausible mechanism preventing this flux-clumping. We find that inflows decrease the amplitude of the axial dipole moment by a ∼ 30 %, relative to a no-inflows scenario. Stronger (weaker) inflows lead to larger (smaller) reductions of the axial dipole moment. The relative amplitude of the generated axial dipole is about 9% larger after very weak cycles than after very strong cycles. This supports the inflows as a non-linear mechanism capable of saturating the global dynamo and contributing to the modulation of the solar cycle within the Babcock-Leighton framework.

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Section: Inflow Parametersmentioning

confidence: 99%

Inflows towards active regions and the modulation of the solar cycle: A parameter study

Martin-Belda

Cameron

2016

A&A

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“…In flux-transport simulations, the inflows to active regions play an important role in the transport of magnetic flux over the course of the solar cycle. The inflows can affect the dispersal of active regions, since they counterbalance the outward diffusion of magnetic flux by convection (De Rosa & Schrijver 2006;Martin-Belda & Cameron 2016). They are also a potential mechanism for modulating the strength of the solar cycle (Cameron & Schüssler 2012;Shetye et al 2015;Martin-Belda & Cameron 2016).…”

Section: Introductionmentioning

confidence: 99%

Measuring solar active region inflows with local correlation tracking of granulation

Löptien

Birch

Duvall

et al. 2017

A&A

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Context. Local helioseismology has detected spatially extended converging surface flows into solar active regions. These play an important role in flux-transport models of the solar dynamo. Aims. We aim to validate the existence of the inflows by deriving horizontal flow velocities around active regions with local correlation tracking of granulation. Methods. We generate a six-year long-time series of full-disk maps of the horizontal velocity at the solar surface by tracking granules in continuum intensity images provided by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). Results. On average, active regions are surrounded by inflows extending up to 10• from the center of the active region of magnitudes of 20-30 m/s, reaching locally up to 40 m/s, which is in agreement with results from local helioseismology. By computing an ensemble average consisting of 243 individual active regions, we show that the inflows are not azimuthally symmetric but converge predominantly towards the trailing polarity of the active region with respect to the longitudinally and temporally averaged flow field.

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“…Corks of opposite polarity that move within 1 Mm of each other are removed from the simulation. The distance threshold is the same as that used by Martin-Belda & Cameron (2016).…”

Section: Cork Simulation For Local Surface Flux Transportmentioning

confidence: 99%

“…Several studies have incorporated inflows around active regions in surface flux transport models (De Rosa & Schrijver 2006;Jiang et al 2010;Cameron & Schüssler 2012;Yeates 2014;Martin-Belda & Cameron 2016. Martin-Belda & Cameron (2016) found that the inflows enhance flux cancellation, and can in conjunction with differential rotation produce a net tilt angle. This tilt is however too small compared with observed tilt angles.…”

Section: Introductionmentioning

confidence: 99%

Testing solar surface flux transport models in the first days after active region emergence

Gottschling,

Schunker,

Birch

et al. 2021

Preprint

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Context. Active regions (ARs) play an important role in the magnetic dynamics of the Sun. Solar surface flux transport models (SFTMs) are used to describe the evolution of the radial magnetic field at the solar surface. The models are kinematic in the sense that the radial component of the magnetic field behaves like passively advected corks. There is however uncertainty about using these models in the early stage of active region evolution, where dynamic effects might be important. Aims. We aim to test the applicability of SFTMs in the first days after the emergence of active regions by comparing them with observations. The models we employ range from passive evolution to models where the inflows around active regions are included. Methods. We simulate the evolution of the surface magnetic field of 17 emerging active regions using a local surface flux transport simulation. The regions are selected such that they do not form fully-fledged sunspots that exhibit moat flows. The simulation includes diffusion and advection by a velocity field, for which we test different models. For the flow fields, we use observed flows from local correlation tracking of solar granulation, as well as parametrizations of the inflows around active regions based on the gradient of the magnetic field. To evaluate our simulations, we measure the cross correlation between the observed and the simulated magnetic field, as well as the total unsigned flux of the ARs, over time. We also test the validity of our simulations by varying the starting time relative to the emergence of flux. Results. We find that the simulations using observed surface flows can reproduce the evolution of the observed magnetic flux. The effect of buffeting of the field by supergranulation can be described as a diffusion process. The SFTM is applicable after 90 % of the peak total unsigned flux of the active region has emerged. Diffusivities in the range between D = 250 to 720 km 2 s −1 are consistent with the evolution of the AR flux in the first five days after this time. We find that the converging flows around emerging active regions are not important for the evolution of the total flux of the AR in these first five days; their effect of increasing flux cancellation is balanced by the decrease of flux transport away from the AR.

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Surface flux transport simulations: Effect of inflows toward active regions and random velocities on the evolution of the Sun’s large-scale magnetic field

Cited by 22 publications

References 26 publications

Inflows towards active regions and the modulation of the solar cycle: A parameter study

Inflows towards active regions and the modulation of the solar cycle: A parameter study

Measuring solar active region inflows with local correlation tracking of granulation

Testing solar surface flux transport models in the first days after active region emergence

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