Can the long-term hemispheric asymmetry of solar activity result from fluctuations in dynamo parameters?

Abstract

The hemispheric asymmetry of sunspot activity observed possesses a regular component varying on a time scale of several solar cycles whose origin and properties are currently debated. This paper addresses the question of whether the long-term hemispheric asymmetry can result from random variations of solar dynamo parameters in time and latitude. Scatter in the observed tilt angles of sunspot groups is estimated to infer constraints on fluctuations in the dynamo mechanism for poloidal field regeneration. A dynamo model with fluctuations in the Babcock-Leighton type $\alpha$-effect is designed in accordance with these constraints and then used to compute a large number of magnetic cycles for statistical analyses of their hemispheric asymmetry. Hemispheric asymmetry in the simulated dynamo results from the presence of an equator-symmetric part in the oscillating magnetic field. The subdominant quadrupolar oscillations are stochastically forced by dominant dipolar oscillations via the equator-symmetric part of the fluctuating $\alpha$-effect. The amplitude and sense of the asymmetry of individual cycles varies on a time scale of the order of four dynamo-cycle periods. The variations are irregular, i.e. not periodic. The model suggests that asymmetry in the polar magnetic fields in the solar minima can be used as a precursor for asymmetry of sunspot activity in the following solar cycle.

Accepted to A&A, 7 two-column pages, 8 figures

References in corpus (7)

• Predicting solar cycle 24 with a solar dynamo model
• Effects of the scatter in sunspot group tilt angles on the large-scale magnetic field at the solar surface
• Turbulent magnetic pumping in a Babcock-Leighton solar dynamo model
• The north-south asymmetry of soft X-ray flare index during solar cycles 21, 22 and 23
• Hemispheric Coupling: Comparing Dynamo Simulations and Observations
• Solar dynamo models with alpha-effect and turbulent pumping from local 3D convection calculations
• How supercritical are stellar dynamos, or why do old main-sequence dwarfs not obey gyrochronology?

Cited by in corpus (8)

• Solar large-scale magnetic field and cycle patterns in solar dynamo
• Long-term Variations in Solar Activity: Predictions for Amplitude and North--South Asymmetry of Solar Cycle 25
• Is the Hemispheric Asymmetry of Monthly Sunspot Area an Irregular Process with Long-Term Memory?
• Dynamo Model for North-South Asymmetry of Solar Activity
• North-South Asymmetry in Solar Activity and Solar Cycle Prediction, V: Prediction for the North-South Asymmetry in the Amplitude of Solar Cycle 25
• Long-term Periodicities in North-South Asymmetry of Solar Activity and Alignments of the Giant Planets
• Hemispheric analysis of the magnetic flux in regular and irregular solar active regions
• Inferring Quadrupolar Dynamo Mode from Sunspot Statistics