Evolution of the Sun's non-axisymmetric toroidal field
arXiv:1703.10075 · doi:10.1051/0004-6361/201730509
Abstract
Aims. We aim to infer the sub-surface distribution of the Sun's non-axisymmetric azimuthal magnetic flux from observable quantities, such as the surface magnetic field and the large scale plasma flows. Methods. We have built a kinematic flux transport model of the solar dynamo based on the Babcock-Leighton framework. We constructed the source term for the poloidal field using SOLIS magnetograms spanning three solar cycles. Based on this source we calculated the azimuthal flux below the surface. The flux transport model has two free parameters which we constrain using sunspot observations from cycle 22. We compared the model results with observations from cycle 23. Results. The structure of the azimuthal field is mainly axisymmetric. The departures from axisymmetry represent, on average, ~3% of the total azimuthal flux. Owing to its relative weakness, the non-axisymmetric structure of the azimuthal field does not have a significant impact on the location in which the emergences appear or on the amount of flux contained in them. We find that the probability of emergence is a function of the ratio between the flux content of an active region and the underlying azimuthal flux.
References in corpus (14)
- Sunspot group tilt angles and the strength of the solar cycle
- Persistent Magnetic Wreaths in a Rapidly Rotating Sun
- The crucial role of surface magnetic fields for the solar dynamo
- Magnetic Wreaths and Cycles in Convective Dynamos
- Obtaining Potential Field Solution with Spherical Harmonics and Finite Differences
- Turbulent magnetic pumping in a Babcock-Leighton solar dynamo model
- Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
- Does the Babcock--Leighton Mechanism Operate on the Sun?
- Small-Scale and Global Dynamos and the Area and Flux Distributions of Active Regions, Sunspot Groups, and Sunspots: A Multi-Database Study
- The radial gradient of the near-surface shear layer of the Sun
- Migration of Ca II H bright points in the internetwork
- The turbulent diffusion of toroidal magnetic flux as inferred from properties of the sunspot butterfly diagram
- An update of Leighton's solar dynamo model
- Surface flux transport simulations: Effect of inflows toward active regions and random velocities on the evolution of the Sun's large-scale magnetic field