Thinkshop12

Solar Cycle Prediction and Reconstruction

David Hathaway (NASA Ames Research Center)

Abstract. Recent observations and analyses strongly indicate that the strength of the sun’s polar fields at the end of a cycle predicts the strength of the next solar cycle. The surface magnetic flux transport that builds up these polar fields is now well observed and can be realistically modeled. Given only the emergence of magnetic flux in active regions, surface flux transport models using the observed near surface flows can reproduce, in detail, the observed magnetic features (including both the polar fields and the large unipolar regions). These surface flux transport models can also be used to predict the strength of the polar fields years before the end of a cycle and thus provide an earlier prediction for the strength of the next cycle. We examine the limits of these predictions by reconstructing the sun’s magnetic field in previous cycles. We find that both the surface flows and the active region sources change systematically over the course (and with the strength) of a cycle and we include those systematic variations in the model. However, stochastic variations in both the flows and the active region sources ultimately limit predictions of the solar cycle.

Invited Review