Exploration with Wavelet Methods

Mid-term variability

Cyclic variation
The SOHO/MDI synoptic maps (to the right) from CR 1911 to 2039 illustrate the magnetic field variation during sunspot cycle 23. Longitudinally averaged magnetic field is shown above (yellow and red mark positive polarity).
The wavelet scalogram of group sunspot number (1610-1995) clearly shows the Maunder Minimum (1645-1715) of very low solar activity. It is also interesting to see how dramatically the solar activity changed after 1940. The wavelet time-scale spectrum of the daily sunspot number 1850-2002 shows the processes behind the variability.
Multi-resolution analysis of C14 production rate. The 22-year cycle is clearly present during the Maunder minimum (zoomed in period) at detail level 4. The 11-year cycle is clearly present during Maunder minimum (zoomed in period) at detail level 3. The magnetic field was too weak to produce sunspots. However magnetic field influencing the cosmic rays existed.

Trends
The wavelet ampligram shows that the solar activity seems to have decreased after 1990. The polar field, assumed to be a precursor of next sunspot cycle's strength, has decreased as seen in a MRA of WSO polar field.

Transients
Scalogram of the group sunspot number (to the left) and the C14 production rate (to the right). A transient seems to occur just after Maunder minimum. A filtering clearly shows the transient.

• Lundstedt, H., Liszka, L. and R. Lundin, Solar Activity Explored with New Wavelet Methods, 23, 1-7, Annal. Geophys., 2005.

• Lundstedt, H., Liszka, R. Lundin and R. Muscheler, Long-Term Solar Activity Explored with Wavelet Methods, Annal. Geophys., 24, 1-9, 2006.