SOLAR-CONSTANT TEMPORAL AND FREQUENCY-CHARACTERISTICS

The Sun's total irradiance at the mean Sun-Earth distance decreased fr om mid-1979 to mid-1987 during the descending part of solar cycle 21. After the minimum had been reached it increased with the onset of cycl e 22 and came to a maximum at mid-1991 during the highest solar activi ty of cycle 22. From the modelized shape of the time signal of the sol ar constant based on the Space Absolute Radiometric Reference (SARR), temporal, amplitude and behaviour characteristics are derived. It is s uggested that the variation observed over a period of more than 14 yea rs is the response of the outer solar layers, the photosphere in parti cular, to some excitation originating somewhere near the bottom of the solar convection zone also responsible for the solar spots and the co rrelated photospheric features. Wavelet analysis and periodiograms are shown for the solar constant and the sunspot index. Their non-station arity is well illustrated as well as strong recurrent periods.