Models for the long-term variations of solar activity

Abstract

One obvious feature of the solar cycle is its variation from one cycle to another. In this article, we review the dynamo models for the long-term variations of the solar cycle. By long-term variations, we mean the cycle modulations beyond the 11-year periodicity and these include, the Gnevyshev-Ohl/Even-Odd rule, grand minima, grand maxima, Gleissberg cycle, and Suess cycles. After a brief review of the observed data, we present the dynamo models for the solar cycle. By carefully analyzing the dynamo models and the observed data, we identify the following broad causes for the modulation: (i) magnetic feedback on the flow, (ii) stochastic forcing, and (iii) time delays in various processes of the dynamo. To demonstrate each of these causes, we present the results from some illustrative models for the cycle modulations and discuss their strengths and weakness. We also discuss a few critical issues and their current trends. The article ends with a discussion of our current state of ignorance about comparing detailed features of the magnetic cycle and the large-scale velocity from the dynamo models with robust observations.

Invited review article for Living Reviews in Solar Physics, in press (53 pages including 25 figures)

References in corpus (52)

• Flux-transport dynamos with Lorentz force feedback on differential rotation and meridional flow: Saturation mechanism and torsional oscillations
• 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
• Solar Cycle Propagation, Memory, and Prediction: Insights from a Century of Magnetic Proxies
• Magnetic Flux Transport at the Solar Surface
• A simulation of convective dynamo in the solar convective envelope: maintenance of the solar-like differential rotation and emerging flux
• Effects of the scatter in sunspot group tilt angles on the large-scale magnetic field at the solar surface
• Solar cyclic activity over the last millennium reconstructed from annual 14C data
• Importance of Meridional Circulation in Flux Transport Dynamo: The Possibility of a Maunder-like Grand Minimum
• Magnetically controlled stellar differential rotation near the transition from solar to anti-solar profiles
• Turbulent magnetic pumping in a Babcock-Leighton solar dynamo model
• Solar Cycle Variability Induced by Tilt Angle Scatter in a Babcock--Leighton Solar Dynamo Model
• Nonlinear current helicity fluxes in turbulent dynamos and alpha quenching
• The Effect of "Rogue" Active Regions on the Solar Cycle
• The Hemispheric Asymmetry of Solar Activity During the Twentieth Century and the Solar Dynamo
• Level and length of cyclic solar activity during the Maunder minimum as deduced from the active day statistics
• Subsurface Meridional Circulation in the Active Belts
• Effects of Meridional Flow Variations on Solar Cycles 23 and 24
• Turbulent Pumping of Magnetic Flux Reduces Solar Cycle Memory and thus Impacts Predictability of the Sun's Activity
• The Waldmeier effect and the flux transport solar dynamo
• Efficient small-scale dynamo in solar convection zone
• Solar differential rotation reproduced with high-resolution simulation
• Observation and Modeling of the Solar-Cycle Variation of the Meridional Flow
• The Role of Subsurface Flows in Solar Surface Convection: Modeling the Spectrum of Supergranular and Larger Scale Flows
• Understanding solar cycle variability
• Five Decades of Chromospheric Activity in 59 Sun-like Stars and New Maunder Minimum Candidate HD 166620
• Long-term modulation of solar cycles
• Nonlinear mechanisms that regulate the solar cycle amplitude
• Re-examining Sunspot Tilt Angle to Include Anti-Hale Statistics
• Polar Network Index as a magnetic proxy for the solar cycle studies
• A theoretical study of the build-up of the Sun's polar magnetic field by using a 3D kinematic dynamo model
• Quenching and anisotropy of hydromagnetic turbulent transport
• Solar activity: intrinsic periodicities beyond 11 years
• How supercritical are stellar dynamos, or why do old main-sequence dwarfs not obey gyrochronology?
• Sunspot tilt angles revisited: Dependence on the solar cycle strength
• A 3D kinematic Babcock Leighton solar dynamo model sustained by dynamic magnetic buoyancy and flux transport processes
• Measurements of Solar Differential Rotation Using the Century Long Kodaikanal Sunspot Data
• Modeling a Maunder Minimum
• Latitude Distribution of Sunspots: Analysis Using Sunspot Data and A Dynamo Model
• Physical link of the polar field build-up with the Waldmeier effect broadens the scope of early solar cycle prediction: Cycle 25 is likely to be slightly stronger than Cycle 24
• Role of observable nonlinearities in solar cycle modulation
• Waldmeier Effect in Stellar Cycles
• Inflows towards active regions and the modulation of the solar cycle: a parameter study
• Hysteresis between distinct modes of turbulent dynamos
• A theoretical model of the variation of the meridional circulation with the solar cycle
• Nature of grand minima and maxima from fully non-linear Flux-Transport Dynamos
• Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: Rotation rate dependence
• Long-term variation in distribution of sunspot groups
• Variational estimation of the large scale time dependent meridional circulation in the Sun: proofs of concept with a solar mean field dynamo model
• Estimating the deep solar meridional circulation using magnetic observations and a dynamo model: a variational approach
• On the possibility of a bimodal solar dynamo
• Active-Region Tilt Angles from White-Light Images and Magnetograms: The Role of Magnetic Tongues

Cited by in corpus (15)

• Turbulent processes and mean-field dynamo
• Analysis of BMR tilt from AutoTAB catalog: Hinting towards the thin flux tube model?
• Predicting the Timing of the the Solar Cycle 25 Polar Field Reversal
• Probing the variations in the timing of the Sun's polar magnetic field reversals through observations and surface flux transport simulations
• Algebraic Quantification of the Contribution of Active Regions to the Sun's Dipole Moment: Applications to Century-scale Polar Field Estimates and Solar Cycle Forecasting
• On the origin of long-term modulation in the Sun's magnetic activity cycle
• Minimal Roles of Solar Subsurface Meridional Flow in the distributed-shear Babcock-Leighton Dynamo
• Hemispheric analysis of the magnetic flux in regular and irregular solar active regions
• Role of sunspot latitude versus tilt in determining the polar field and amplitude of the next cycle: Cause of the weak Solar Cycle 20
• Observed Joys law of Bipolar Magnetic Region tilts at the emergence supports the thin flux tube model
• Observation-Based Iterative Map for Solar Cycles. I. Nature of Solar Cycle Variability
• Cyclic sunspot activity during the first millennium CE as reconstructed from radiocarbon
• Breaking gyrochronology through the collapse of coronal winds
• Solar Cycle Prediction: Challenges, Progress, and Future Perspectives
• Stellar cycle variability in Mount Wilson stars and dynamo models: Rotation rate and dynamo number dependency