Space Climate 7 Meeting Abstract
How many active regions are needed to predict the solar dipole moment?
Anthony R Yeates (Durham University, UK)
T. Whitbread (Durham University, UK) A. Munoz-Jaramillo (Southwest Research Institute, USA)
Recent studies suggest that individual "rogue" active regions can lead to significant fluctuations in the Sun's polar magnetic field strength, and hence in the amplitude of future solar cycles. In particular, it has been hypothesized that the unusually weak polar field at the end of Cycle 23 was caused by a small number of large, abnormally oriented active regions near the equator. We have tested these claims using a data-driven surface flux transport model, based on NSO synoptic magnetograms. In particular, we have isolated the contributions of each observed active region to the Sun's end-of-cycle axial dipole, for Cycles 21-24. The results do indeed show that the most significant contributors for Cycle 23 weakened the dipole. On the other hand, we show that an accurate estimate of the end-of-cycle dipole moment cannot ignore the cumulative contribution of many weaker regions. For a given active region, its end-of-cycle contribution is determined by two factors: its initial dipole moment and its latitude of emergence.
Mode of presentation: oral (Need to be confirmed by the SOC)