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The polar field reversal is a crucial process in the cyclic evolution of thelarge-scale magnetic field of the Sun.Various important characteristics of asolar cycle, such as its duration and strength, and also the cyclepredictability, are determined by the polar field reversal time. While theregular measurements of solar magnetic field have been accumulated for morethan half a century, there is no consensus in the heliophysics communityconcerning the interpretation of the Sun's polar field measurements andespecially the determination of polar field reversal time. There exists asevere problem of non-reproducibility in the reported results even from studiesof the same observational dataset, and this causes an obstacle to make moreaccurate forecasts of solar cycle. Here, we analyze the solar magnetograms fromfour instruments for the last four cycles, to provide a more correctinterpretation of the polar field observations and to find more accurate timeof the reversals. We show the absence of triple (multipolar) reversals inCycles 21 - 24, significant variations in the time interval between reversalsin the hemispheres and in the time interval between a reversal and a cyclebeginning. In order to understand the origin of the reversal time variation, weperform Surface Flux Transport (SFT) simulations and find out that the presenceof the 'anomalous' bipolar magnetic regions (BMRs) in different phases of acycle can cause cycle-to-cycle variations of the reversal time within thesimilar range found in observations.

Probing the variations in the timing of the Sun's polar magnetic field reversals through observations and surface flux transport simulations