| Long-term solar activity has been studied with a set of wavelet methods. The
following indicators of long-term solar activity were used; the group sunspot
number, the sunspot number, and the 14C production rate. Scalograms
showed the very long-term scales of 2300 years (Hallstat cycle),
900-1000 years, 400-500 years, and 200 years (de Vries cycle). Scalograms
of a newly-constructed 14C production rate showed interesting solar modulation
during the Maunder minimum. Multi-Resolution Analysis (MRA) revealed the
modulation in detail, as well as peaks of solar activity not seen in the sunspot
number. In both the group sunspot number scalogram and the 14C
production rate scalogram, a process appeared, starting or ending in late 1700. This
process has not been discussed before. Its solar origin is unclear.
The group sunspot number ampligram and the sunspot number ampligram showed the
Maunder and the Dalton minima, and the period of high solar activity, which
already started about 1900 and then decreased again after mid 1990. The
decrease starts earlier for weaker components. Also, weak semiperiodic
activity was found.
Time Scale Spectra (TSS) showed both deterministic and stochastic processes
behind the variability of the long-term solar activity. TSS of the 14C
production rate, group sunspot number and Mt. Wilson sunspot index and plage
index were compared in an attempt to interpret the features and processes
behind the long-term variability. |