Quenching of Meridional Circulation in Flux Transport Dynamo Models

Abstract

Guided by the recent observational result that the meridional circulation of the Sun becomes weaker at the time of the sunspot maximum, we have included a parametric quenching of the meridional circulation in solar dynamo models such that the meridional circulation becomes weaker when the magnetic field at the base of the convection zone is stronger. We find that a flux transport solar dynamo tends to become unstable on including this quenching of meridional circulation if the diffusivity in the convection zone is less than about 2 × 10 11 cm 2 s −1 . The quenching of α, however, has a stabilizing effect and it is possible to stabilize a dynamo with low diffusivity with sufficiently strong α-quenching. For dynamo models with high diffusivity, the quenching of meridional circulation does not produce a large effect and the dynamo remains stable. We present a solar-like solution from a dynamo model with diffusivity 2.8 × 10 12 cm 2 s −1 in which the quenching of meridional circulation makes the meridional circulation vary periodically with solar cycle as observed and does not have any other significant effect on the dynamo.

Is meridional circulation important in modelling irregularities of the solar cycle?

“…However we fail to reproduce these results in a low diffusivity model. Therefore this study along with some other studies (Chatterjee, Nandy & Choudhuri 2004;Chatterjee & Choudhuri 2006;Choudhuri & Karak 2009;Goel & Choudhuri 2009;Hotta & Yokoyama 2010;Karak & Choudhuri 2012) supports the high diffusivity model for the solar cycle.…”

“…Bidya Karak: There is an indication that the meridional circulation has a periodic variation with the solar cycle becoming stronger during solar minimum and weaker during solar maximum. It is not clear whether this variation is coming due to the active regions or due to the Lorentz force of the magnetic field acting on the velocity field (Karak & Choudhuri 2012). As the meridional circulation is coming from a slight imbalance between two large terms, we expect the meridional circulation to vary cycle to cycle stochastically.…”

Magnetically controlled stellar differential rotation near the transition from solar to anti-solar profiles

“…This kind of weak anti-correlation between the activity cycle and the meridional flow has been found in solar observations (Chou & Dai 2001;Hathaway & Rightmire 2010) and is believed to arise at least in part from the Lorentz force of the dynamo-generated magnetic fields (see, e.g., Rempel 2006, Karak & Choudhuri 2012, Passos et al 2012). The meridional circulation at the bottom is also weakly correlated with the activity cycle (correlation A26, page 11 of 17 A&A 576, A26 (2015) coefficients between B and u θ (0.73 R , ±32…”

Magnetic activity and solar-like pulsations of X-ray sources in the Kepler field of view

“…In the same time, though, the magnetic field quenches the amplitude of those oscillations (Karak & Choudhuri 2012). Therefore, it is very interesting to study the trade-off between these two physical phenomena which are also closely related to our ability to derive the basic physical parameters of cool stars.…”