A Babcock–leighton Solar Dynamo Model With Multi-Cellular Meridional Circulation in Advection- And Diffusion-Dominated Regimes

Abstract

Babcock-Leighton type solar dynamo models with single-celled meridional circulation are successful in reproducing many solar cycle features. Recent observations and theoretical models of meridional circulation do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular circulation patterns in a Babcock-Leighton solar dynamo in advection-and diffusiondominated regimes. We show from simulations that presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of butterfly wing to an anti-solar type. A butterfly diagram constructed from middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a meridional circulation containing four cells in latitude behaves distinctly differently in the two regimes, producing solar-like butterfly diagrams with fast cycles in the higher diffusivity regime, and complex branches in butterfly diagrams in the lower diffusivity regime. We also find that dynamo solutions for a four-celled pattern, two in radius and two in latitude, prefer to quickly relax to quadrupolar parity if the bottom flow-speed is strong enough, of similar order of magnitude as the surface flow-speed.

Statistical properties of solar Hα flare activity

“…Belucz & Dikpati (2013) found that the hemispheric asymmetry of solar magnetic activity depends on the differences in the amplitude of the meridional circulations in those hemispheres. Belucz et al (2015) demonstrated that the effect of greater inflows into active region belts in one hemisphere could make the activity level in that hemisphere larger compare to the other hemisphere. They also found that the dominance of one hemisphere could last for more than one solar cycle.…”

Solar Cycle Variability Induced by Tilt Angle Scatter in a Babcock–Leighton Solar Dynamo Model

“…In the absence of this information and to make contact with previous BL dynamo models, we have retained the single-celled profile. Others have investigated the role of multi-celled circulation profiles in 2D BL/flux transport dynamo models and they have demonstrated that these models are still viable, provided that the circulation near the base of the convection zone is equatorward and that the convective transport of poloidal flux (typically parameterized by a turbulent diffusion and a magnetic pumping) is sufficiently efficient (Jouve & Brun 2007;Hazra et al 2014;Belucz et al 2015;Hazra & Nandy 2016).…”

The Life Cycle of Active Region Magnetic Fields

“…These studies dispute the reported detection of multiple cells structure in depth (Zhao et al 2013) and in latitude (Schad et al 2013;Zhao et al 2013). The implications of multiple meridional cells for flux-transport dynamos have been explored by Hazra et al (2014) and Belucz et al (2015).…”