Sun's inertial motion and luminosity

Fast Fourier analysis of the detrended record of solar irradiance obtained by the Nimbus-7 cavity pyrheliometer shows a rich spectrum of significant frequencies between about 30 and 850 nHz (periods between 13 and 400 days). Wolff and Hickey (1987), elaborating on a model developed by Wolff (1974, 1976, 1983, and 1984), suggest that many of these peaks arise due to interference of rigidly rotating global solar oscillations (r- and g-modes). Their model fit is quite good in the region above about 135 nHz, but less satisfactory below this threshold. It is noted that the FFT spectrum of d-sq L/d-sq t, the second derivative of angular momentum of the solar inertial motion, contains peaks matching the large peaks in the irradiance spectrum below 400 nHz with periods near 0.08, 0.24, 0.65, and about 1 yr. The origins of the peaks in the d-sq L/d-sq t spectra are discussed, and some previous studies are reviewed bearing on the question of a possible relationship of solar motion and solar activity.