The interaction of new and old magnetic fluxes at the beginning of solar cycle 23

The 11 yr cycle of solar activity follows Hale's law by reversing the magne tic polarity of leading and following sunspots in bipolar regions during th e minima of activity. In the 1996-1997 solar minimum, most solar activity e merged in narrow longitudinal zones-"active longitudes" but over a range in latitude. Investigating the distribution of solar magnetic flux, we have f ound that the Hale sunspot polarity reversal first occurred in these active zones. We have estimated the rotation rates of the magnetic flux in the ac tive zones before and after the polarity reversal. Comparing these rotation rates with the internal rotation inferred by helioseismology, we suggest t hat both "old" and "new" magnetic fluxes were probably generated in a low-l atitude zone near the base of the solar convection zone. The reversal of ac tive region polarity observed in certain longitudes at the beginning of a n ew solar cycle suggests that the phenomenon of active longitudes may give f undamental information about the mechanism of the solar cycle. The nonrando m distribution of old-cycle and new-cycle fluxes presents a challenge for d ynamo theories, most of which assume a uniform longitudinal distribution of solar magnetic fields.