Variability of the solar “constant” on time scales of minutes to years

Solar irradiance variability has been studied from measurements of total solar irradiance at 1 AU, the solar ''constant'' S/sub 0/, since the late 1960s. Power spectra of time series from satellite and balloon experiments show that the irradiance varies, with periods of minutes to several hours and with amplitudes of parts per million to a few hundreths of a percent. Part of this variance is due to coherent pressure and, possibly, gravity oscillations as spherical harmonics of the sun. On time scales of days to months most of the variance is a modulation of the solar irradiance by photospheric features related to solar activity and reaches amplitudes of a few tenths of a pecent. Because of its origin the variance in this range changes by up to 1 order of magnitude with the solar cycle, as shown by comparison of the power spectra from 1980 and 1984/1985, respectively. The first evidence of a persistent long-term change comes from satellite data, which show a downward trend of S/sub 0/ since 1980 by about 0.02% per year. The S/sub 0/ determinations between 1967 and 1970, compared with the modern ones show a statistically significant increase during that period of similar magnitude. Bothmore » trends together could be part of a 22-year cycle related to the magnetic cycle of the sun. copyright American Geophysical Union 1987« less

[1]  J. Toomre,et al.  Seismology of the Sun , 1985, Science.

[2]  T. H. Vonder Haar,et al.  Initial Solar Irradiance Determinations from Nimbus 7 Cavity Radiometer Measurements , 1980, Science.

[3]  R. Willson.  New radiometric techniques and solar constant measurements , 1973 .

[4]  H. B. Vanderraay,et al.  Global solar oscillations in irradiance and velocity: A comparison , 1984 .

[5]  K. Kondratyev,et al.  Solar radiation and solar activity , 1970 .

[6]  Eric Fossat,et al.  Full-disk observations of solar oscillations from the geographic South Pole: Latest results , 1983 .

[7]  P. Delache,et al.  Long period oscillations in solar diameter measurements , 1985, Nature.

[8]  S. Sofia,et al.  Solar irradiance modulation by active regions from 1969 through 1980 , 1981 .

[9]  R. Willson.  Solar total irradiance observations by Active Cavity Radiometers , 1981 .

[10]  C. Fröhlich.  Solar variability for periods of days to months , 1984 .

[11]  K. Kondratyev,et al.  The Stratospheric Mechanism of Solar and Anthropogenic Influences on Climate , 1979 .

[12]  R. Willson,et al.  Active cavity radiometer type IV. , 1979, Applied optics.

[13]  Philip H. Scherrer,et al.  Detection of solar gravity mode oscillations , 1983, Nature.

[14]  H. Hudson,et al.  Long-Term Downward Trend in Total Solar Irradiance , 1986, Science.

[15]  D. Hoyt,et al.  Solar irradiance modulation by active regions from 1969 through 1981 , 1983 .

[16]  Claus Fröhlich,et al.  Solar Gravity Modes from Acrim/smm Irradiance Data , 1988 .

[17]  D. Murcray,et al.  Change in the solar constant between 1968 and 1978 , 1979 .

[18]  E. Rhodes,et al.  Solar p-mode oscillations as a tracer of radial differential rotation , 1979 .

[19]  Richard C. Willson,et al.  The effects of sunspots on solar irradiance , 1982 .

[20]  C. Fröhlich,et al.  OBSERVED RELATION BETWEEN SOLAR LUMINOSITY AND RADIUS , 1984 .

[21]  Gary A. Chapman,et al.  On the energy balance of solar active regions , 1984, Nature.

[22]  G A Chapman,et al.  Observations of solar irradiance variability. , 1981, Science.

[23]  P. Foukal,et al.  A thermal model of sunspot influence on solar luminosity , 1983 .

[24]  P. Foukal,et al.  The influence of faculae on total solar irradiance and luminosity , 1986 .

[25]  C. Wolff.  The rotational spectrum of g-modes in the sun , 1983 .

[26]  D. Murcray,et al.  The measurement of the solar constant from high altitude balloons , 1969 .

[27]  G. Kanbach,et al.  A 154-day periodicity in the occurrence of hard solar flares? , 1984, Nature.

[28]  Richard C. Willson,et al.  Measurements of solar total irradiance and its variability , 1984 .

[29]  A. Drummond,et al.  New Value for the Solar Constant of Radiation , 1968, Nature.