  The Schwabe (~11 yr) value for the annual sunspot number is sometimes
uncritically applied to other measures of solar activity, direct and indirect,
including the 10.7 cm radio flux, the inflow of galactic cosmic rays, solar
flare frequency, terrestrial weather, and components of space climate, with the
risk of a resulting loss of information. The ruling (Babcock) hypothesis and
its derivatives link the sunspot cycle to dynamo processes mediated by
differential solar rotation, but despite 60 years of observation and analysis
the ~11 yr periodicity remains difficult to model; the possible contribution of
planetary dynamics is undergoing a revival. The various solar sequences that
genuinely display an ~11 yr cycle stand to benefit from an understanding of its
periodicity that goes beyond statistical kinship. The outcome could ironically
prompt the demotion of sunspots from their dominant historical role in favour
of other possible indicators of solar cyclicity, such as the solar wind flux
and its isotopic signatures, even if they are less accessible.
