Flux-Transport Dynamos with Lorentz Force Feedback on Differential Rotation and Meridional Flow: Saturation Mechanism and Torsional Oscillations

By Matthias Rempel. 2006

202 citations recorded by the source corpus.

In this paper we discuss a dynamic flux-transport dynamo model that includes the feedback of the induced magnetic field on differential rotation and meridional flow. We consider two different approaches for the feedback: mean field Lorentz force and quenching of transport coefficients such as turbulent viscosity and heat conductivity. We find that even strong feedback on the meridional flow does not change the character of the flux-transport dynamo significantly; however, it leads to a significant reduction of differential rotation. To a large degree independent of the dynamo parameters, the saturation takes place when the toroidal field at the base of the convection zone reaches between 1.2 and 1.5 T, and the energy converted into magnetic energy corresponds to about 0.1%-0.2% of the solar luminosity. The torsional oscillations produced through Lorentz force feedback on differential rotation show a dominant poleward propagating branch with the correct phase relation to the magnetic cycle. We show that incorporating enhanced surface cooling of the active region belt (as proposed by Spruit) leads to an equatorward propagating branch in good agreement with observations.

Subfields: Astronomy and Astrophysics, Computational Mechanics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/3bbb0254421d2db13daf2f4ae44c42d4342b0159

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Computational Mechanics

In Molecular Biology

Citations in the corpus

The Magnetic Landscape of the Sun's Polar Region (2008, background): “We however recognize that there would remain a serious energetics problem if the toroidal field strength indeed reached 100 kG (Schüssler 1996; Rempel 2006).”
NUMERICAL SIMULATIONS OF QUIET SUN MAGNETISM: ON THE CONTRIBUTION FROM A SMALL-SCALE DYNAMO (2014, methodology): “Compared to that the energy extracted from large-scale mean flows in mean field dynamo models (Rempel 2006) as well as 3D global dynamo simulations (Nelson et al. 2013) is about 2 orders of magnitude smaller.”
Solar Dynamo Theory (2014, methodology): “Figure produced from numerical data provided by Arnab Rai Choudhuri (IIS, Bangalore). also on the magnetic backreaction on the meridional flow and how it affects dynamo action in flux transport dynamos in general (Rempel 2006b, Karak & Choudhuri 2012, Passos et al. 2012).”
Simulating and Predicting Solar Cycles Using a Flux-Transport Dynamo (2006, background): “With respect to magnetic feedbacks, Rempel et al. (2005) and Rempel (2006) have shown that while changes in the differential rotation should be small (essentially the torsional oscillations) due to these feedbacks, and therefore unlikely to change the forecast, changes in the meridional circulation…”
Magnetic Fields in the Solar Convection Zone (2004, background): “(1) Recent solar cycle dynamo models which take into account the dynamic effects of the Lorentz force from the large-scale mean fields have suggested that the toroidal magnetic field generated at the base of the solar convection zone is ∼ 1.5 × 104 G (Rempel, 2006b).”
Sunspot Group Tilt Angles and the Strength of the Solar Cycle (2010, background): “Some models suggest that both components of the inflow are driven by the excess cooling associated with plage (Spruit, 2003; Rempel, 2006).”
Simulations of Dynamo Action in Fully Convective Stars (2007, background): “Alternatively, it has been argued that coherent meridional circulations may bring fields to the surface (e.g., Rempel 2006; Dikpati & Charbonneau 1999).”
MAGNETIC CYCLES IN A CONVECTIVE DYNAMO SIMULATION OF A YOUNG SOLAR-TYPE STAR (2011, background): “…solar dynamo models where the advection of toroidal flux by the meridional circulation regulates cyclic activity (e.g., Wang & Sheeley 1991; Dikpati & Charbonneau 1999; Küker et al. 2001; Nandy & Choudhuri 2001; Dikpati & Gilman 2006; Rempel 2006; Jouve & Brun 2007; Yeates et al. 2008).”