Exploring the Physical Basis of Solar Cycle Predictions: Flux Transport Dynamics and Persistence of Memory in Advection- versus Diffusion-dominated Solar Convection Zones

By A. Robin Yeates, Dibyendu Nandy, D. Mackay. 2007

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The predictability, or lack thereof, of the solar cycle is governed by numerous separate physical processes that act in unison in the interior of the Sun. Magnetic flux transport and the finite time delay that it introduces, specifically in the so-called Babcock-Leighton models of the solar cycle with spatially segregated source regions for the α- and Ω-effects, play a crucial rule in this predictability. Through dynamo simulations with such a model, we study the physical basis of solar cycle predictions by examining two contrasting regimes, one dominated by diffusive magnetic flux transport in the solar convection zone, the other dominated by advective flux transport by meridional circulation. Our analysis shows that diffusion plays an important role in flux transport, even when the solar cycle period is governed by the meridional flow speed. We further examine the persistence of memory of past cycles in the advection- and diffusion-dominated regimes through stochastically forced dynamo simulations. We find that in the advection-dominated regime this memory persists for up to three cycles, whereas in the diffusion-dominated regime this memory persists for mainly one cycle. This indicates that solar cycle predictions based on these two different regimes would have to rely on fundamentally different inputs, which may be the cause of conflicting predictions. Our simulations also show that the observed solar cycle amplitude-period relationship arises more naturally in the diffusion-dominated regime, thereby supporting those dynamo models in which diffusive flux transport plays a dominant role in the solar convection zone.

Subfields: Astronomy and Astrophysics, Molecular Biology, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/349758b10cc06d8b3987ba1aabd88903d536332c

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Citations in the corpus

Solar Dynamo Theory (2014, background): “Substantial efforts are underway to understand and improve the predictive capabilities of this type of forecasting scheme (e.g., Yeates et al. 2008, Karak & Nandy 2012, Dikpati & Anderson 2012, Muñoz-Jaramillo et al. 2013).”
Data Assimilation in the ADAPT Photospheric Flux Transport Model (2014, unknown): “At the same time, a problem in photosphere forecasting noted previously [46, 30] is loss of balance in magnetic ﬂux when assimilating large solar active regions on the boundary of the observation region.”
The Solar Cycle (2007, result): “Yeates et al. (2008) compared an advection-dominated model like that of Dikpati et al. (2006) to a diffusiondominated models like that of Choudhuri et al. (2007) and concluded that the diffusion-dominated model was better because it gave a better fit to the relationship between meridional flow…”
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).”
Solar Forcing for CMIP6 (v3.1) (2016, background): “In stochastically forced kinematic dynamo models, persistence in the solar-cycle-averaged level of activity (hereafter “memory”) can extend from less than one and up to three cycles, depending on details of the models and of the physical parameter regime in which they operate (e.g., St-Jean and Char”
ON THE WEAKENING OF THE POLAR MAGNETIC FIELDS DURING SOLAR CYCLE 23 (2009, background): “…next cycle are generated by converting the pre-existing poloidal field into toroidal flux (Cameron & Schüssler 2007; Choudhuri et al. 2007; Dikpati 2008; Dikpati & Gilman 2006; Dikpati et al. 2006, 2008; Hathaway 2009; Schatten 2005; Svalgaard et al. 2005; Wang & Sheeley 2009; Yeates et al. 2008).”