Periodicities of Solar Irradiance and Solar Activity Indices - Part One
Abstract
Using a standard FFT time series analysis, our results show an 8-11 months periodicity in the solar total and UV irradiances, 10.7 cm radio flux, Ca-K plage index, and sunspot blocking function. The physical origin of this period is not known, but the evidence in the results exclude the possibility that the observed period is a harmonic due to the FFT transform or detrending. Periods at 150-157 and 51 days are found in those solar data which are related to strong magnetic fields. The 51-day period is the dominant period in the projected areas of developing complex sunspot groups, but it is missing from the old decaying sunspot areas. This evidence suggests that the 51-day period is related to the emergence of new magnetic fields. A strong 13.5-day period is found in the total irradiance and projected areas of developing complex groups. This confirms those results (e.g., Donnelly et al., 1983, 1984; Bai, 1987, 1989) which show that `active centers' are located 180 deg apart from each other.
- Publication:
-
Solar Physics
- Pub Date:
- September 1990
- DOI:
- 10.1007/BF00154372
- Bibcode:
- 1990SoPh..129..165P
- Keywords:
-
- Solar Activity Effects;
- Solar Magnetic Field;
- Solar Radiation;
- Solar Rotation;
- Ultraviolet Radiation;
- Fast Fourier Transformations;
- Solar Cycles;
- Time Series Analysis;
- Solar Physics;
- Solar Cycle;
- Projected Area;
- Solar Irradiance;
- Strong Magnetic Field;
- Sunspot Group