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

TL;DR

This study compares flux transport regimes in solar dynamo models, revealing that advection and diffusion dominance affect cycle memory and amplitude-period relationships, impacting predictability of solar cycles.

Contribution

It provides a detailed analysis of how diffusive versus advective flux transport regimes influence solar cycle predictability and memory, supported by dynamo simulations.

Findings

Memory persists for up to three cycles in advection-dominated regimes.

Memory persists for mainly one cycle in diffusion-dominated regimes.

Observed amplitude-period relationship aligns more with diffusion-dominated models.

Abstract

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 it introduces, specifically in the so-called Babcock-Leighton models of the solar cycle with spatially segregated source regions for the alpha and omega 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.