Polar Field Puzzle: Solutions from Flux-Transport Dynamo and Surface Transport Models

Abstract

Polar fields in solar cycle 23 were about 50% weaker than those in cycle 22. The only theoretical models which have addressed this puzzle are surface transport models and flux-transport dynamo models. Comparing polar fields obtained from numerical simulations using surface flux transport models and flux-transport dynamo models, we show that both classes of models can explain the polar field features within the scope of the physics included in the respective models. In both models, how polar fields change as a result of changes in meridional circulation depends on the details of meridional circulation profile used. Using physical reasoning and schematics as well as numerical solutions from a flux-transport dynamo model, we demonstrate that polar fields are determined mostly by the strength of surface poloidal source provided by the decay of tilted, bipolar active regions. Profile of meridional flow with latitude and its changes with time have much less effect in flux-transport dynamo models than in surface transport models.

ApJ (accepted)

References in corpus (10)

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• The unusual minimum of sunspot cycle 23 a consequence of Sun's meridional plasma flow variations
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• Helioseismic data inclusion in solar dynamo models
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• Large-scale horizontal flows in the solar photosphere II: Long-term behaviour and magnetic activity response

Cited by in corpus (11)

• Meridional Circulation in Solar and Stellar Convection Zones
• On differential rotation and overshooting in solar-like stars
• Solar Magnetic Field Reversals and the Role of Dynamo Families
• A 3D Babcock-Leighton Solar Dynamo Model
• Solar magnetic activity cycles, coronal potential field models and eruption rates
• A coupled $2\times 2$D Babcock-Leighton solar dynamo model. II. Reference dynamo solutions
• A Three-Dimensional Babcock-Leighton Solar Dynamo Model: Initial Results with Axisymmetric Flows
• Evolution of active and polar photospheric magnetic fields during the rise of Cycle 24 compared to previous cycles
• The Role of the Magnetorotational Instability in the Sun
• Effects of turbulent pumping on stellar activity cycles
• Time-dependent theory of solar meridional flows