The Polar Field Reversal Process over Five Solar Cycles

We examine the process during which the solar magnetic field reverses polarity around each solar maximum. We use the McIntosh Archive (McA) of solar synoptic maps over five consecutive solar cycles, SCs 19 – 23, or from 1955 to 2009. This data set allows us to track features such as filaments, polarity inversion lines (PILs), coronal hole (CH) boundaries, and sunspots over many consecutive Carrington rotations (CRs) and solar cycles (SCs). The McA allows tracking of the evolution of the polar magnetic regions and how the rush-to-the-pole (RttP) patterns occur during the period when the polar fields reverse around each activity maximum. We use the McA dataset to determine the timing and lags among these events around the maximum of each SC in each hemisphere: the sunspot number peak, the polarity reversal, the disappearance of the polar crown filaments and PILs, the poleward movement of midlatitude CHs of new-cycle polarity behind the primary PIL, the first appearance of polar CHs of new-cycle polarity, and the earliest persistent complete coverage of each pole by a CH. The goal is to use the RttPs and CH boundary mapping to better constrain solar interior and dynamo models. The end of the PIL RttP, the end of the RttP of the poleward boundary of new-cycle polarity midlatitude CHs, and the first appearance of new-cycle polar CHs are nearly coincident and follow the polarity reversals in each hemisphere by about 1 year. We also show the lag times relative to “terminator” times, which denote when the toroidal magnetic flux built during a given cycle is canceled across the equator, thus beginning the rise of new-cycle flux. This occurs after the start of the RttPs of the polar CH boundaries and near the start of the primary and secondary PIL RttPs. The start of the RttP of the poleward boundary of the new-cycle, midlatitude CH that leads to the new polar CH always occurs later than the terminator time, so the terminator is located near the beginning of the ascending phase.