Abstract
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 (1987a, b), elaborating on a model developed by Wolff (1974a, b, 1976, 1983, 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. We note that the FFT spectrum of d2 L/d2 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. We discuss the origins of the peaks in the d2 L/d2t spectra and review some previous studies bearing on the question of a possible relationship of solar motion and solar activity. The future persistence of the observed spectral peaks of irradiance with periods near 0.24 and 0.65 yr will provide a key test for this hypothesis.
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