Total solar irradiance trend during solar cycles 21 and 22

Science

Volumn 277, Issue 5334, 1997, Pages 1963-1965

  Willson, Richard C ^a  

^a NASA Goddard Institute for Space Studies   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CLIMATE CHANGE; IRRADIANCE; SOLAR CYCLE; SOLAR RADIATION;

ARTICLE; ENVIRONMENTAL TEMPERATURE; GLOBAL CLIMATE; GREENHOUSE EFFECT; PRIORITY JOURNAL; RADIATION DETECTOR; SOLAR RADIATION;

EID: 0030881118     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.277.5334.1963     Document Type: Article

References (20)

1. R. C. Willson, in The Sun as a Variable Star, International Astronomical Union Colloquium 143 Proceedings, J. Pap, C. Fröhlich, H. Hudson, K. Solanki, Eds. (Cambridge Univ. Press, New York, 1994), pp. 54-62.
2. J. A. Eddy, Science 192, 1189 (1976).
3. P. E. Damon and C. P. Sonett, in The Sun in Time, C. P. Sonett, M. S. Giampapa, M. S. Mathews, Eds. (Univ. of Arizona Press, Tucson, AZ, 1991), pp. 360-388.
4. R. C. Willson and H. S. Hudson, Nature 351, 42 (1991).
5. D. Hoyt and L. Kyle, in Proc. Climate Impact of Solar Variability (NASA Conf. Rep. 3086, NASA, Greenbelt, MD, 1990), pp. 293-300.
6. R. B. Lee III, M. A. Gibson, R. S. Wilson, S. Thomas, J. Geophys. Res. 100, 1667 (1995).
7. R. C. Willson and H. S. Hudson, Nature 332, 810 (1988).
8. ACRIM II results are reported on the ACRIM I scale using the ACRIM I/ACRIM II ratio (1.001689) derived in the text.
9. R. C. Willson, S. Gulkis, M. Janssen, H. S. Hudson, G. A. Chapman, Science 211, 700 (1981).
10. The ERB and ERBS experiments view the sun as it passes through their fields of view for only a few minutes per orbit, whereas the ACRIM experiments are solar-pointed for at least 10 shutter cycles per orbit, every orbit, every day. During most of the ERB mission, observations were made every orbit on 3 of every 4 days. The ERBS experiments observe the sun for a few minutes during one orbit every 2 weeks.
11. UV irradiances, their surrogates (Hel 1083 and F10.7 cm fluxes), and the Zurich sunspot number were at a minimum in mid-1996, ACRIM II results showed a local minimum near the same time. The broad TSI minimum of solar cycle 21 was centered about 6 months before solar minimum, as defined by reversal of active-region magnetic polarity in September 1986. Definition of the actual location of the cycle 22 TSI minimum must await analysis of the 1997 ACRIM II results.
12. H. L. Kyle, D. V. Hoyt, J. R. Hickey, B. J. Vallette, Nimbus-7 Earth Radiation Budget Calibration History - Part I: The Solar Channels (NASA Ref. Pub. 1316, NASA, Greenbelt, MD, 1993), p. 27.
13. A. T. Mecherikunnel, Sol. Phys. 155, 211 (1994).
14. H. L. Kyle et al., Nimbus-7 Earth Radiation Budget Compact Solar Data Set User's Guide (NASA Ref. Pub. 1346, NASA, Greenbelt, MD, 1994).
15. Degradation of the cavity sensors of TSI experiments is a phenomenon that usually occurs in two phases. The first is rapid degradation that occurs when the cavity's solar flux-absorbing surface is modified by its initial exposure to space and the radiation environment. The sensors then settle into a "mission" degradation modality as further exposure to solar flux slowly alters the cavity's absorbing surfaces. The rates of initial and mission degradation vary between experiments, but the degradation phenomena are common to most of them. It was further observed in the ACRIM I experiment that the rate of degradation was proportional to both the amount of solar exposure and the relative abundance of high energy, short-wavelength flux. During periods of intense solar magnetic activity, the enhanced amounts of high-energy, short-wavelength solar radiation increase the rate of degradation.
16. A lower susceptibility for ERB to accelerated degradation would be expected because of its longer history of solar exposure, including the peak activity period of solar cycle 21. Its sensor surfaces may have been near their degradation saturation point during solar cycle 22.
17. R. C. Willson, paper presented at American Geophysical Union meeting, Baltimore, MD, May 1997.
18. D. Rind and J. Overpeck, Quat. Sci. Rev. 12, 347 (1993).
19. National Research Council, Solar Influences on Global Change (National Academy Press, Washington, DC, 1994), pp. 36-40.
20. I thank J. Hansen, L. Kyle, A. Mecherikunnel, R. Lee III, and R. Wilson for providing helpful discussions, documentation, data, and advice. The ACRIM II experiment is supported by NASA at Columbia University under NASA contract NAS5-97164. The ACRIM II results are available from the NASA Goddard Space Flight Center and Langley Research Center Distributed Active Archive Centers.