GONG p-Mode Parameters Through Two Solar Cycles

We investigate the parameters of global solar p-mode oscillations, namely damping width Gamma, amplitude A, mean squared velocity < v(2)>, energy E, and energy supply rate dE/dt, derived from two solar cycles' worth (1996 - 2018) of Global Oscillation Network Group (GONG) time series for harmonic degrees l = 0 - 150. We correct for the effect of fill factor, apparent solar radius, and spurious jumps in the mode amplitudes. We find that the amplitude of the activity-related changes of Gamma and A depends on both frequency and harmonic degree of the modes, with the largest variations of Gamma for modes with 2400 mu Hz <= nu <= 3300 mu Hz and 31 <= l <= 60 with a minimum-to-maximum variation of 26.6 +/- 0.3% and of A for modes with 2400 mu Hz <= nu <= 3300 mu Hz and 61 <= l <= 100 with a minimum-to-maximum variation of 27.4 +/- 0.4%. The level of correlation between the solar radio flux F-10.7 and mode parameters also depends on mode frequency and harmonic degree. As a function of mode frequency, the mode amplitudes are found to follow an asymmetric Voigt profile with nu(max) = 3073.59 +/- 0.18 mu Hz. From the mode parameters, we calculate physical mode quantities and average them over specific mode frequency ranges. In this way, we find that the mean squared velocities < v(2)> and energies E of p modes are anticorrelated with the level of activity, varying by 14.7 +/- 0.3% and 18.4 +/- 0.3%, respectively, and that the mode energy supply rates show no significant correlation with activity. With this study we expand previously published results on the temporal variation of solar p-mode parameters. Our results will be helpful to future studies of the excitation and damping of p modes, i.e., the interplay between convection, magnetic field, and resonant acoustic oscillations.