Physical Models for Solar Cycle Predictions

Abstract

The dynamic activity of stars such as the Sun influences (exo)planetary space environments through modulation of stellar radiation, plasma wind, particle and magnetic fluxes. Energetic solar-stellar phenomena such as flares and coronal mass ejections act as transient perturbations giving rise to hazardous space weather. Magnetic fields – the primary driver of solar-stellar activity – are created via a magnetohydrodynamic dynamo mechanism within stellar convection zones. The dynamo mechanism in our host star – the Sun – is manifest in the cyclic appearance of magnetized sunspots on the solar surface. While sunspots have been directly observed for over four centuries, and theories of the origin of solar-stellar magnetism have been explored for over half a century, the inability to converge on the exact mechanism(s) governing cycle to cycle fluctuations and inconsistent predictions for the strength of future sunspot cycles have been challenging for models of the solar cycles. This review discusses observational constraints on the solar magnetic cycle with a focus on those relevant for cycle forecasting, elucidates recent physical insights which aid in understanding solar cycle variability, and presents advances in solar cycle predictions achieved via data-driven, physics-based models. The most successful prediction approaches support the Babcock-Leighton solar dynamo mechanism as the primary driver of solar cycle variability and reinforce the flux transport paradigm as a useful tool for modelling solar-stellar magnetism.

Solar Cycle Observations

“…The peak in the polar field strength typically occurs at or just before solar cycle minimum. The amplitude of the Sun's polar fields (as measured by the (Schatten et al 1978;Svalgaard et al 2005;Petrovay 2010;Muñoz-Jaramillo et al 2013;Bhowmik et al 2023). This can be understood in terms of the dynamo model proposed by Babcock (1961) and extended by Leighton (1964).…”

Simplified Model of the Solar Magnetic Field

“…Based on this, a logical connection arises with a decrease in temperature on Earth during the same period. Furthermore, since both the number of sunspots and the distribution of nutation and their energies in the period of 1805-1816 are extremely similar to the results of 2014-2023, we can assume that the distribution of the field in 1805-1816 is similar to the field in Figure 19. Self-oscillating model of sunspot quantities for a 2000 yr period.…”

Predicting the Timing of the Solar Cycle 25 Polar Field Reversal

“…Understanding solar activity cycle variability has been a persistent problem in the field of solar physics. Despite over a century of dedicated solar observations, this puzzle has yet to be resolved, and our understanding of the solar activity cycle remains incomplete (see Karak 2023 andBhowmik et al 2023). The intimate relation between the solar cycle and the polar field of the Sun was first suggested by Babcock (1959) and put forward by Babcock (1961) as the foundation of solar dynamo models (see Charbonneau 2010 for extensive review on the dynamo models).…”