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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 surfacetransport models and flux-transport dynamo models. Comparing polar fieldsobtained from numerical simulations using surface flux transport models andflux-transport dynamo models, we show that both classes of models can explainthe polar field features within the scope of the physics included in therespective models. In both models, how polar fields change as a result ofchanges in meridional circulation depends on the details of meridionalcirculation profile used. Using physical reasoning and schematics as well asnumerical solutions from a flux-transport dynamo model, we demonstrate thatpolar fields are determined mostly by the strength of surface poloidal sourceprovided by the decay of tilted, bipolar active regions. Profile of meridionalflow with latitude and its changes with time have much less effect influx-transport dynamo models than in surface transport models.

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