Solar Cycle Prediction with the Advective Flux Transport (AFT) Code

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 is realistically modeled with the Advective Flux Transport (AFT) code. Given the emergence of magnetic flux in active regions, and using the observed near surface flows, the AFT code can reproduce, in detail, the observed magnetic features - including both the polar fields and the large unipolar regions – years later. The AFT code can thus be used to predict the strength of the polar fields years before the end of a cycle and thereby 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 of a cycle and with the strength of a cycle. However, stochastic variations in both the flows and the active region sources ultimately limit predictions of the solar cycle.