Target Description: This task challenges proposers to characterize the properties of the solar dynamo that determine the strength of the solar activity cycle and its terrestrial consequences (e.g,. through irradiance changes and geomagnetic effects). Recent advances in modeling promise to provide accurate forecasts of the strength and timing of solar cycles. Now Cycle 23, a longer than average and somewhat peculiar cycle, is ending, and the new Cycle 24, which has widely different predictions for its maximum activity level from different models, is beginning. In order to be useful for future cycle forecasting, models need to be constrained and related more closely to LWS impacts. Interpretation of available data from the SOlar and Heliospheric Observatory (SOHO), Global Oscillation Network Group (GONG), Synoptic Optical Long-term Investigations of the Sun (SOLIS), other space- and ground-based sources, and the upcoming Solar Dynamics Observatory (SDO) mission toward this resolution is timely and may lead to new observational strategies as the solar activity level increases.

Goals and Measures of Success: Successful investigations should help us to discriminate between and improve dynamo models. This requires improved measurements of critical subsurface flows, including the expected deep meridional flow, detection of the subsurface magnetic fields, and a determination of the influences of the solar polar properties on the dynamo. The connections between dynamo operation and the properties of the active regions that give rise to terrestrial effects also require clarification. Solar irradiance variations are determined by both sunspot and plage areas. What in the dynamo action determines this combination? Similarly, significant eruptive events can occur during both large and small activity cycles. An understanding of what aspect of dynamo action gives rise to eruptive regions is needed.

Types of investigations:
• Development of methods to discriminate between subsurface magnetic fields and thermal structures;
• Determination of the properties of the deep meridional return flow;
• Analyses revealing how the magnetic and dynamic characteristics of the solar poles affect the dynamo and the solar activity cycle; and
• Use of observations to discriminate between models that forecast the properties of Cycle 24.