First Tabulation of the Sunspot-cycle Start in the Seventeen Cycles Since the Cycle’s Discovery: Consequences for the Solar Dynamo?

Abstract In the seventeen Cycles 8–24 the first new-cycle sunspot group is tabulated for the first time in each solar hemisphere (thirty-four groups). This allows the determination of the central-value of two parameters of the sunspot-cycle start, as a hemispheric average, since the cycle’s discovery two hundred years ago: first emergence epoch and latitude. The tabulation uses the state-of-the-art cycle-separation data obtained by R. Leussu et al. As a median over the seventeen cycles, the first group is found to have emerged 1.4 yr before sunspot minimum. Its median unsigned latitude is 27 15, lower than in an earlier estimate by A. P. Kramynin & F. A. Mikhalina based on only thirteen groups. This initial median latitude is similar to the ≈27 0 group latitude found by other authors at sunspot minimum epoch. If reproduced, this finding could result in a new observational constraint on solar-dynamo models.