The Global Solar Dynamo

Abstract

A brief summary of the various observations and constraints that underlie solar dynamo research are presented. The arguments that indicate that the solar dynamo is an alpha-omega dynamo of the Babcock-Leighton type are then shortly reviewed. The main open questions that remain are concerned with the subsurface dynamics, including why sunspots emerge at preferred latitudes as seen in the familiar butterfly wings, why the cycle is about 11 years long, and why the sunspot groups emerge tilted with respect to the equator (Joy's law). Next, we turn to magnetic helicity, whose conservation property has been identified with the decline of large-scale magnetic fields found in direct numerical simulations at large magnetic Reynolds numbers. However, magnetic helicity fluxes through the solar surface can alleviate this problem and connect theory with observations, as will be discussed.

Accepted in Space Science Reviews NORDITA-2015-97

References in corpus (29)

• Global-Scale Turbulent Convection and Magnetic Dynamo Action in the Solar Envelope
• Simulations of nonhelical hydromagnetic turbulence
• Predicting solar cycle 24 with a solar dynamo model
• Persistent Magnetic Wreaths in a Rapidly Rotating Sun
• Magnetic Landscape of Sun's Polar Region
• 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
• The unusual minimum of sunspot cycle 23 a consequence of Sun's meridional plasma flow variations
• On the Formation of Active Regions
• The cause of the weak solar cycle 24
• Origins of Rolling, Twisting and Non-Radial Propagation of Eruptive Solar Events
• Helioseismic Imaging of Fast Convective Flows Throughout the Near-Surface Shear Layer
• Small-scale magnetic helicity losses from a mean-field dynamo
• Meridional Flow in the Solar Convection Zone II: Helioseismic Inversions of GONG Data
• The Waldmeier effect and the flux transport solar dynamo
• The Mount Wilson Ca II K index
• On the cause of solar-like equatorward migration in global convective dynamo simulations
• The Role of Subsurface Flows in Solar Surface Convection: Modeling the Spectrum of Supergranular and Larger Scale Flows
• Turbulent dynamo with advective magnetic helicity flux
• Solar supergranulation revealed by granule tracking
• Magnetic helicity fluxes in an alpha-squared dynamo embedded in a halo
• Intense bipolar structures from stratified helical dynamos
• Observations and modelling of North-South asymmetries using a Flux Transport Dynamo
• Magnetic twist: a source and property of space weather
• Digitization of sunspot drawings by Spörer made in 1861-1894
• The critical role of magnetic helicity in astrophysical large-scale dynamos
• Time-distance helioseismology: A new averaging scheme for measuring flow vorticity

Cited by in corpus (26)

• The Solar Orbiter mission -- Science overview
• Solar cycle prediction
• The Polarimetric and Helioseismic Imager on Solar Orbiter
• Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)
• Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude
• Physical Models for Solar Cycle Predictions
• The relative emission from chromospheres and coronae: dependence on spectral type and age
• A Relationship between the Solar Rotation and Activity Analysed by Tracing Sunspot Groups
• Dynamo saturation through the latitudinal variation of bipolar magnetic regions in the Sun
• Solar meridional circulation from twenty-one years of SOHO/MDI and SDO/HMI observations: Helioseismic travel times and forward modeling in the ray approximation
• Latitude Distribution of Sunspots: Analysis Using Sunspot Data and A Dynamo Model
• The Ca II H&K Rotation-Activity Relation in 53 mid-to-late type M-Dwarfs
• Temporal evolutions and quasi-periodic variations present in the sunspot number and group sunspot area data measured at Kodaikanal Observatory for solar cycles 14 to 24
• Long-Term Variations in Solar Differential Rotation and Sunspot Activity, II: Differential Rotation Around the Maxima and Minima of Solar Cycles 12-24
• On the Rotation of the Solar Chromosphere
• Chromospheric Synoptic Maps of Polar Crown Filaments
• Loss of toroidal magnetic flux by emergence of bipolar magnetic regions
• Evidence of strong relationship between hemispheric asymmetry in solar coronal rotation and solar activity during solar cycle 24
• Hale cycle in solar hemispheric radio flux and sunspots: Evidence for a northward shifted relic field
• Application and interpretation of deep learning for identifying pre-emergence magnetic-field patterns
• A journey of exploration to the polar regions of a star: probing the solar poles and the heliosphere from high helio-latitude
• Contemporaneous Observations of $H\alpha$ Luminosities and Photometric Amplitudes for M Dwarfs
• Periodic variation and phase analysis of grouped solar flare with sunspot activity
• Sunstardb: a database for the study of stellar magnetism and the solar-stellar connection
• Centennial solar EUV irradiance from ionospheric currents: Varying sunspot-EUV irradiance relation and modified spot-facula ratio
• A study of global magnetic helicity in self-consistent spherical dynamos