A New Tool for Predicting the Solar Cycle: Correlation Between Flux Transport at the Equator and the Poles

Abstract

Magnetic flux cancellation on the Sun plays a crucial role in determining the way in which the net magnetic flux changes in every solar cycle, affecting the large scale evolution of the coronal magnetic field and heliospheric environment. We have investigated the correlation between the solar magnetic flux cancelled at the equator and the solar magnetic flux transported to the poles by comparing the net amount of magnetic flux in the latitude belt 0^∘ – 5^∘ to that of 45^∘ – 60^∘ and 55^∘ – 90^∘, using synoptic magnetograms from the National Solar Observatory at Kitt Peak, during Solar Cycles 21 – 24. We find a good correlation between the net flux in the latitude bands 0^∘ – 5^∘ and 55^∘ – 90^∘ when the net flux for the northern and southern hemispheres are considered together. In addition, we have investigated the correlation between the net flux cancelled at the equator during each cycle and the strength of solar polar field at each cycle minimum and we find a good correlation between the two. We discuss the implication of the correlation between the flux transported across the equator and to the poles, which has an important bearing in the estimation of the residual polar cap field strength at the cycle minimum. This can be used as a predictive tool for estimating the amplitude of subsequent cycles, and we use it to estimate a maximum smoothed sunspot number of 76 ± 5 and 85 ± 5 for the northern and southern hemispheres, respectively, for the upcoming Solar Cycle 25.