Bipolar Magnetic Regions on the Sun: Global Analysis of the SOHO/MDI Data Set
arXiv:1112.5226 · doi:10.1088/0004-637X/745/2/129
Abstract
The magnetic flux that is generated by dynamo inside the Sun emerges in the form of bipolar magnetic regions. We have analyzed the whole set of solar magnetograms obtained with the SOHO/MDI instrument in 1995-2011, and automatically identified 160,079 bipolar magnetic regions that span a range of scale sizes across nearly four orders of magnitude. Their properties have been statistically analyzed, in particular with respect to the polarity orientations of the bipolar regions, including their tilt angle distributions. The latitude variation of the average tilt angles (with respect to the E-W direction), known as Joy's law, is found to closely follow the relation 32.1*sin(latitude)[deg]. There is no indication of a dependence on region size that one may expect if the tilts were produced by the Coriolis force during the buoyant rise of flux loops from the tachocline region. A few percent of all regions have orientations that violate Hale's polarity law. We show examples, from different phases of the solar cycle, where well defined medium-size bipolar regions with opposite polarity orientations occur side by side in the same latitude zone. Such oppositely oriented large bipolar regions cannot be part of the same toroidal flux system, but different flux systems must coexist in the same latitude zones. These examples are incompatible with the paradigm of coherent, subsurface toroidal flux ropes as the source of sunspots, and instead show that fluctuations must play a major role at all scales for the turbulent dynamo. We see no observational support for a separation of scales or a division between a global and a local dynamo, since also the smallest scales in the data set retain a non-random component that significantly contributes to the accumulated emergence of a N-S dipole moment that leads to the replacement of the old global poloidal field with a new one that has the opposite orientation.
38 pages, 9 figures; to appear in the Astrophysical Journal
References in corpus (3)
Cited by in corpus (94)
- The Solar Cycle
- Flare-productive active regions
- The crucial role of surface magnetic fields for the solar dynamo
- Magnetic Wreaths and Cycles in Convective Dynamos
- 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
- The cause of the weak solar cycle 24
- Solar magnetic fields as revealed by Stokes polarimetry
- Predicting the Amplitude and Hemispheric Asymmetry of Solar Cycle 25 with Surface Flux Transport
- Solar Cycle Variability Induced by Tilt Angle Scatter in a Babcock--Leighton Solar Dynamo Model
- Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
- Recovering Joys Law as a Function of Solar Cycle, Hemisphere, and Longitude
- A 3D Babcock-Leighton Solar Dynamo Model
- Emergence of magnetic flux generated in a solar convective dynamo. I: Formation of Sunspots and Active regions, and Origin of Their Asymmetries
- Coronal Magnetic Field Evolution from 1996 to 2012: Continuous Non-Potential Simulations
- Effects of Meridional Flow Variations on Solar Cycles 23 and 24
- Comparing Simulations of Rising Flux Tubes Through the Solar Convection Zone with Observations of Solar Active Regions: Constraining the Dynamo Field Strength
- Long-Term Measurements of Sunspot Magnetic Tilt Angles
- Solar magnetic activity cycles, coronal potential field models and eruption rates
- Kinematic active region formation in a three-dimensional solar dynamo model
- A coupled D Babcock-Leighton solar dynamo model. II. Reference dynamo solutions
- Measurements of Photospheric and Chromospheric Magnetic Fields
- Models for the long-term variations of solar activity
- Double-peaks of the solar cycle: An explanation from a dynamo model
- Basal magnetic flux and the local solar dynamo
- Re-examining Sunspot Tilt Angle to Include Anti-Hale Statistics
- Statistical Analysis of Filament Features Based on the Hα Solar Images from 1988 to 2013 by Computer Automated Detection Method
- Chirality of High Latitude Filaments over Solar Cycle 23
- A new dynamo pattern revealed by the tilt angle of bipolar sunspot groups
- Magnetic field dependence of bipolar magnetic region tilts on the Sun: Indication of tilt quenching
- A Three-Dimensional Babcock-Leighton Solar Dynamo Model: Initial Results with Axisymmetric Flows
- Studies of grand minima in sunspot cycles from a flux transport solar dynamo model
- A theoretical study of the build-up of the Sun's polar magnetic field by using a 3D kinematic dynamo model
- Mean field models of flux transport dynamo and meridional circulation in the Sun and stars
- Evolution of active and polar photospheric magnetic fields during the rise of Cycle 24 compared to previous cycles
- Comparison of Debrecen and Mount Wilson/Kodaikanal sunspot group tilt angles and the Joy's law
- Relationships Between Characteristics of the Line-of-Sight Magnetic Field and Solar Flare Forecasts
- Tilt of sunspot bipoles in Solar Cycles 15 to 24
- Recovery from Maunder-like Grand Minima in a Babcock--Leighton Solar Dynamo Model
- Active region formation through the negative effective magnetic pressure instability
- How many active regions are necessary to predict the solar dipole moment?
- Scaling laws for magnetic fields on the quiet Sun
- How good is the bipolar approximation of active regions for surface flux transport?
- Dynamo saturation through the latitudinal variation of bipolar magnetic regions in the Sun
- A Systematic Study of Hale and Anti-Hale Sunspot Physical Parameters
- Sunspot areas and tilt angles for solar cycles 7-10
- Torus-Stable Zone Above Starspots
- Sunspot tilt angles revisited: Dependence on the solar cycle strength
- Intense bipolar structures from stratified helical dynamos
- Observations and modelling of North-South asymmetries using a Flux Transport Dynamo
- Solar large-scale magnetic field and cycle patterns in solar dynamo
- Sunrise III: Overview of Observatory and Instruments
- Latitude Distribution of Sunspots: Analysis Using Sunspot Data and A Dynamo Model
- Average motion of emerging solar active region polarities II: Joy's law
- Solar Anti-Hale Bipolar Magnetic Regions: A Distinct Population with Systematic Properties
- Different contributions to space weather and space climate from different big solar active regions
- Bipolar region formation in stratified two-layer turbulence
- Evidence of active MHD instability in EULAG-MHD simulations of solar convection
- Is the Hemispheric Asymmetry of Monthly Sunspot Area an Irregular Process with Long-Term Memory?
- Evolution of the Sun's Polar-fields and the Poleward Transport of Remnant Magnetic Flux
- Impact of Anomalous Active Regions on the Large-scale Magnetic Field of the Sun
- Analysis of BMR tilt from AutoTAB catalog: Hinting towards the thin flux tube model?
- AutoTAB: Automatic Tracking Algorithm for Bipolar Magnetic Regions
- Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: Rotation rate dependence
- Dynamo Saturation in Rapidly Rotating Solar-Type Stars
- Predicting the Timing of the the Solar Cycle 25 Polar Field Reversal
- A Catalog of Bipolar Active Regions Violating the Hale Polarity Law, 1989-2018
- Surface flux concentrations and spherical alpha-square dynamo
- Exploring Bistability in the Cycles of the Solar Dynamo through Global Simulations
- The Properties of the Tilts of Bipolar Solar Regions
- A mechanism for the dependence of sunspot group tilt angles on cycle strength
- Effects of Radiative Diffusion on Thin Flux Tubes in Turbulent Solar-like Convection
- Incorporating Surface Convection into a 3D Babcock-Leighton Solar Dynamo Model
- Magnetic fluxes of solar active regions of different magneto-morphological classes: I. Cyclic variations
- Synthetic solar cycle for active regions violating the Hale's polarity law
- On effects of surface bipolar magnetic regions on the convection zone dynamo
- A new simple dynamo model for stellar activity cycle
- Active-Region Tilt Angles from White-Light Images and Magnetograms: The Role of Magnetic Tongues
- Recent advances in the 3D kinematic Babcock-Leighton solar dynamo modeling
- Three-dimensional non-kinematic simulation of post-emergence evolution of bipolar magnetic regions and Babcock-Leighton dynamo of the Sun
- Naked emergence of an anti-Hale active region I. Overall evolution and magnetic properties
- Subcritical dynamo and hysteresis in a Babcock-Leighton type kinematic dynamo model
- Role of sunspot latitude versus tilt in determining the polar field and amplitude of the next cycle: Cause of the weak Solar Cycle 20
- Observation-Based Iterative Map for Solar Cycles. I. Nature of Solar Cycle Variability
- Observed Joys law of Bipolar Magnetic Region tilts at the emergence supports the thin flux tube model
- Estimates of current helicity and tilt of solar active regions and Joy's law
- Advances in mean-field dynamo theories
- Solar active region scaling laws revisited
- Solar Interior
- Solar Cycle Prediction: Challenges, Progress, and Future Perspectives
- Predicting a solar cycle before its onset using a flux transport dynamo model
- Evolution of the Sun's activity and the poleward transport of remnant magnetic flux in Cycles 21--24
- Long-term variability of the solar cycle in the Babcock-Leighton dynamo framework