The emerging features of bipolar magnetic regions during solar minima

Solar magnetic synoptic charts obtained by NSO/Kitt Peak and SOHO/MDI are analyzed in order to study the appearance of bipolar magnetic regions (BMRs) during solar minima. We find that the emergence of long-lived BMRs have three typical features. (1) The emergence rate of BMRs in the new cycle increases about 3 times faster than the rate of the old cycles decreases. (2) Two consecutive solar cycles have an overlapping period of near 10 Carrington rotations. During this very short overlapping time interval, BMRs of two cycles tend to concentrate in the same longitudes. (3) About 53% BMRs distribute with a longitudinal distance of 1/8 solar rotation. Such phenomena suggests a longitudinal mode of m = 8 existing during solar minima.