Long period fluctuations of solar active regions

Abstract

The fluctuation spectra of solar active regions (ARs) contain information about the geometrical features and ground physical processes responsible for the appearance of such a background vibration noise. The investigation is based on an analysis of a time series built photospheric magnetograms and comprises case studies of several types of AR structures. We detect characteristic properties of Fourier and wavelet spectra evaluated for the solar active region area and radial magnetic flux time series. There are long-period oscillations, similarly to the characteristic lifetimes of super-granulation, determined from the datasets of the AR total area and radial magnetic flux, respectively. According to our results the fluctuation spectra of the AR areas and radial magnetic fluxes somewhat differ from each other both in terms of values of the spectral power-law exponents, as well as their variability ranges in different consider cases. The characteristic properties of the area and radial magnetic flux fluctuation spectra for the Ars show noticeable discrepancies between each other. It can also be concluded that behind the formation of AR area and radial flux vibration spectra might be different physical mechanisms in action.