A New Formula for Predicting Solar Cycles

Abstract

© 2019. The American Astronomical Society. All rights reserved.. A new formula for predicting solar cycles based on the current theoretical understanding of the solar cycle from the flux transport dynamo is presented. Two important processes - fluctuations in the Babcock-Leighton (BL) mechanism and variations in the meridional circulation (MC), which are believed to be responsible for irregularities of the solar cycle - are constrained using observational data. We take the polar field near minima of the cycle as a measure of the randomness in the BL process, and the decay rate near the minima as a consequence of the change in MC. We couple these two observationally derived quantities into a single formula to predict the amplitude of the future solar cycle. Our new formula suggests that cycle 25 would be a moderate cycle. Whether this formula for predicting the future solar cycle can be justified theoretically is also discussed using simulations from the flux transport dynamo model.