Exploration with Wavelet Methods

Short-term variability

Cyclic variation
The solar magnetic mean field (SMMF) observed at WSO (Stanford) is plotted for the period May 16, 1975 to March 13, 2001. Below is the wavelet power spectra shown. Several peaks for scales 13.5, 27, 155 days and 1.3-2 years are visible.

Transients
Multi-resolution analysis (to the left) of 20 degrees south latitude and longitudes 250-300 degrees of synoptic map (above) for CR 2009. It is a study of active region (AR) 486. MRA describes nicely the flux distribution and changes at different scales.
The wavelet power spectra seem to show peaks at times of coronal mass ejections (CMEs).

SOHO/MDI mean field data of one minute time resolution was used.

The top panel shows the sum of 53 wavelet power spectra at times of CMEs. The arrow indicates the onset of a CME.

The panel below shows the sum of 23 wavelet power spectra at times of no CMEs.


Boberg, F., Lundstedt, H., Hoeksema, J,T., Scherrer, P.H. and W.Lui, Solar mean magnetic field variability: A wavelet approach to Wilcox Solar Observatory and SOHO/Michelson Doppler Imager observations, Journal of Geophysical Research, Vol. 107, No A10,1318, 15-1--15-7, 2002.