The Polar Field Reversal Process over Five Solar Cycles Using the McIntosh Archive

We study the polar magnetic field reversal process over five solar cycles (SCs 19-23, Dec. 1954 - Aug. 2009) using the recently digitized McIntosh Archive (McA) of solar synoptic maps. This data set allows the tracking of features such as filaments, polarity inversion lines (PILs), coronal hole boundaries and sunspots over many consecutive Carrington rotations. Here we follow the evolution of the polar magnetic regions of the Sun and how the rush-to-the-poles and other patterns occur during the period when the polar fields reverse around each SC maximum. This process was first studied in detail for SCs 20 and 21 by Webb et al. (1984). The goal then as now is to use the rush-to-the-poles and CH boundary mapping to better constrain solar interior and dynamo models. We use the McA data sets 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 PIL, the first appearance of mid-latitude CHs of new-cycle polarity, and the earliest complete coverage of each pole by a coronal hole. With the newly processed McA, we can now extend this type of study over five consecutive SCs through SC 23.