The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations

Abstract

A theory of the mean tilt of sunspot bipolar regions (the angle between a line connecting the leading and following sunspots and the solar equator) is developed. A mechanism of formation of the mean tilt is related to the effect of Coriolis force on meso-scale motions of super-granular convection and large-scale meridional circulation. The balance between the Coriolis force and the Lorentz force (the magnetic tension) determines an additional contribution caused by the large-scale magnetic field to the mean tilt of the sunspot bipolar regions at low latitudes. The latitudinal dependence of the solar differential rotation affects the mean tilt which can explain deviations from the Joy's law for the sunspot bipolar regions at high latitudes. The obtained theoretical results and performed numerical simulations based on the nonlinear mean-field dynamo theory which takes into account conservation of the total magnetic helicity and the budget equation for the evolution of the Wolf number density, are in agreement with observational data of the mean tilt of sunspot bipolar regions over individual solar cycles 15 - 24.

arXiv comment12 pages, 4 figures, mn2e.cls , revised, final version

References in corpus (29)

• Astrophysical magnetic fields and nonlinear dynamo theory
• Predicting solar cycle 24 with a solar dynamo model
• Sunspot group tilt angles and the strength of the solar cycle
• Nonlinear theory of a "shear-current" effect and mean-field magnetic dynamos
• Magnetic Helicity Tensor for an Anisotropic Turbulence
• Magnetic fluctuations and formation of large-scale inhomogeneous magnetic structures in a turbulent convection
• Recovering Joys Law as a Function of Solar Cycle, Hemisphere, and Longitude
• The Role of Magnetic Helicity Transport in Nonlinear Galactic Dynamos
• Magnetic Helicity Evolution During the Solar Activity Cycle: Observations and Dynamo Theory
• Detection of negative effective magnetic pressure instability in turbulence simulations
• The Radial Distribution of Magnetic Helicity in the Solar Convective Zone: Observations and Dynamo Theory
• The Sun's Preferred Longitudes and the Coupling of Magnetic Dynamo Modes
• Re-examining Sunspot Tilt Angle to Include Anti-Hale Statistics
• A new dynamo pattern revealed by the tilt angle of bipolar sunspot groups
• Nonlinear Magnetic Diffusion and Magnetic Helicity Transport in Galactic Dynamos
• Nonlinear Turbulent Magnetic Diffusion and Mean-Field Dynamo
• Bipolar magnetic structures driven by stratified turbulence with a coronal envelope
• Tilt of sunspot bipoles in Solar Cycles 15 to 24
• Current helicity of active regions as a tracer of large-scale solar magnetic helicity
• Self-assembly of shallow magnetic spots through strongly stratified turbulence
• Tilt Angle and Footpoint Separation of Small and Large Bipolar Sunspot Regions Observed with HMI
• Mean-field and direct numerical simulations of magnetic flux concentrations from vertical field
• Recovering Solar Toroidal Field Dynamics From Sunspot Location Patterns
• Magnetic concentrations in stratified turbulence: the negative effective magnetic pressure instability
• Bipolar region formation in stratified two-layer turbulence
• Effects of large-scale non-axisymmetric perturbations in the mean-field solar dynamo
• The dynamics of Wolf numbers based on nonlinear dynamo with magnetic helicity: comparisons with observations
• The Properties of the Tilts of Bipolar Solar Regions
• Nonlinear mean-field dynamo and prediction of solar activity

Cited by in corpus (8)

• Sunspot tilt angles revisited: Dependence on the solar cycle strength
• Turbulent processes and mean-field dynamo
• Impact of Anomalous Active Regions on the Large-scale Magnetic Field of the Sun
• Turbulent magnetic helicity fluxes in solar convective zone
• On effects of surface bipolar magnetic regions on the convection zone dynamo
• Budget equations and astrophysical nonlinear mean-field dynamos
• Magnetic fields of low-mass main sequences stars: Nonlinear dynamo theory and mean-field numerical simulations
• Estimates of current helicity and tilt of solar active regions and Joy's law