Dynamics of periodicities of global activity indices associated with solar rotation in cycle 27.

Periodicities of global activity indices associated with solar rotation using frequency-time analysis are studied. As a consequence of solar rotation, dynamic spectra of the global indices in the range of periods 10 - 40 days, to a greater extent, reflect the spatial structure of magnetic fields and its variations as compared to time variations as such. Dynamic spectra of the mean magnetic field of the Sun, of sunspot relative numbers, and of the radio emission flux density at the frequency of 2800 MHz show a typical drift in periods which corresponds to the Spörer law. Analysis of fluctuations of the indices reveals quasi-periodic displacements in the distribution of local maxima of the dynamic spectrum with respect to their mean position, with a period of about two years. Such displacements reflect oscillations of the mean latitude of the sunspot formation area and are, possibly, associated with the modulating effect of global convection.