Top left: dependence of the instantaneous oscillation period upon the instantaneous oscillation amplitude in mode 8 shown inthe right-hand panel of Fig. 2. The red solid line indicates the best fit of the empirical period-amplitude dependence by a power-law function (see Sect. 3 for the fitting details). Top right: dependence of the instantaneous period of mode 8 upon the long-term trend of the average magnetic field signal, shown in the right-hand panel of Fig. 1. The red curve shows the best fit of the empirical dependence by the power law function with the index of –3/2. Bottom left: dependence of the instantaneous period of mode 8 upon the long-term variation of the normalised line-of-sight magnetic flux of the structure, projected onto the plane of sky. Bottom right: dependence of the instantaneous period of mode 8 upon the long-term trend of the total area signal, shown in the right-hand panel of Fig. 1.