On the origin of long-term modulation in the Sun's magnetic activity cycle

Abstract

One of the most striking manifestations of orderly behavior emerging out of complex interactions in any astrophysical system is the 11-year cycle of sunspots. However, direct sunspot observations and reconstructions of long-term solar activity clearly exhibit amplitude fluctuations beyond the decadal timescale -- which may be termed as supradecadal modulation. Whether this long-term modulation in the Sun's magnetic activity results from nonlinear mechanisms or stochastic perturbations remains controversial and a matter of active debate. Utilizing multi-millennial scale kinematic dynamo simulations based on the Babcock-Leighton paradigm -- in the likely (near-critical) regime of operation of the solar dynamo -- we demonstrate that this supradecadal modulation in solar activity cannot be explained by nonlinear mechanisms alone; stochastic forcing is essential for the manifestation of observed long-term fluctuations in the near-critical dynamo regime. Our findings substantiate some independent observational and theoretical investigations, and provide additional insights into temporal dynamics associated with a plethora of natural phenomena in astronomy and planetary systems arising from weakly nonlinear, non-deterministic processes.

12 pages, 4 figures, Published in ApJL

References in corpus (14)

• Understanding space weather to shield society: A global road map for 2015-2025 commissioned by COSPAR and ILWS
• Exploring the Physical Basis of Solar Cycle Predictions: Flux Transport Dynamics and Persistence of Memory in Advection versus Diffusion Dominated Solar Convection Zones
• The crucial role of surface magnetic fields for the solar dynamo
• The Sun is less active than other solar-like stars
• Solar cyclic activity over the last millennium reconstructed from annual 14C data
• Solar Cycle Variability Induced by Tilt Angle Scatter in a Babcock--Leighton Solar Dynamo Model
• The Effect of "Rogue" Active Regions on the Solar Cycle
• On the astronomical origin of the Hallstatt oscillation found in radiocarbon and climate records throughout the Holocene
• Understanding solar cycle variability
• Long-term modulation of solar cycles
• Nonlinear mechanisms that regulate the solar cycle amplitude
• Solar activity: intrinsic periodicities beyond 11 years
• Quantifying the Anisotropy and Solar Cycle Dependence of "$1/f$" Solar Wind Fluctuations Observed by Ace
• Evidence of persistence of weak magnetic cycles driven by meridional plasma flows during solar grand minima phases