Surveys in Geophysics

, Volume 33, Issue 3–4, pp 453–473

Total Solar Irradiance Observations



The record of total solar irradiance (TSI) during the past 35 years has overlapping observations from space which can be merged to a composite, and three are available, namely the PMOD, the ACRIM and the IRMB composites. There are important differences between them, which are discussed in detail in order to find the best representation of solar variability during the last three cycles, for the following discussions of solar irradiance variability. Moreover, the absolute value of TSI from TIM on SORCE is 1,361 Wm−2, substantially lower than the value 1,365 Wm−2, which was observed by the classical radiometers. New results from specific experiments are now available, which are discussed in order to define the value to be used in, e.g., climate models. The most important issue regarding the recent TSI records is the low value observed during the minimum in 2009, which is 25% of a typical cycle amplitude lower than the value in 1996. The validity of this low value has been confirmed by comparing all existing TSI observations during cycle 23. On the other hand, activity indices, such as the sunspot number, the 10.7-cm radio flux (F10.7), the CaII and MgII indices and also the Ly-α irradiance or the frequency changes in low-order p modes, show a much smaller decreases relative to their respective typical cycle amplitude. It is most likely that an increasing contrast of the facular and network elements with decreasing magnetic field is responsible for this discrepancy. The value of TSI at minima is correlated with the open magnetic field of the Sun, BR, at minima. Using BR at minima, interpolated linearly in between as a fourth component of a proxy model based on the photometric sunspot index and on the MgII index improves the explanation of the variance of TSI over the full period of the last three solar cycles to 84.7%. Results from other models are also discussed.


Total solar irradiance Solar variability Solar activity 


  1. Baliunas S, Jastrow R (1990) Evidence for long-term brightness changes of solar-type stars. Nature 348:520–523CrossRefGoogle Scholar
  2. Ball WT, Unruh YC, Krivova NA, Solanki S, Harder JW (2011) Solar irradiance variability: a six-year comparison between SORCE observations and the SATIRE model. Astron Astrophys 530:A71. doi:10.1051/0004-6361/201016189 CrossRefGoogle Scholar
  3. Bertello L, Ulrich RK, Boyden JE (2010) The mount Wilson Ca ii K plage index time series. Sol Phys 264:31–44. doi:10.1007/s11207-010-9570-z CrossRefGoogle Scholar
  4. Broomhall A, Chaplin WJ, Elsworth Y, Fletcher ST, New R (2009) Is the current lack of solar activity only skin deep? Astrophys J 700:162–165. doi:10.1088/0004-637X/700/2/L162 CrossRefGoogle Scholar
  5. Brusa RW, Fröhlich C (1986) Absolute radiometers (PMO6) and their experimental characterization. Appl Opt 25:4173–4180. doi:10.1364/AO.25.004173 CrossRefGoogle Scholar
  6. Dewitte S, Crommelynck D, Mekaoui S, Joukoff A (2004) Measurement and uncertainty of the long-term total solar irradiance trend. Sol Phys 224:209–216. doi:10.1007/s11207-005-5698-7 CrossRefGoogle Scholar
  7. Foukal P, Milano L (2001) A measurement of the quiet network contribution to solar irradiance variation. Geophys Res Lett 28:883–886. doi:10.1029/2000GL012072 CrossRefGoogle Scholar
  8. Foukal P, Ortiz A, Schnerr R (2011) Dimming of the 17th century sun. Astrophys J 733:38. doi:10.1088/2041-8205/733/2/L38 CrossRefGoogle Scholar
  9. Foukal PV, Lean J (1988) Magnetic modulation of solar luminosity by photospheric activity. Astrophys J 328:347–357. doi:10.1086/166297 CrossRefGoogle Scholar
  10. Foukal PV, Lean J (1990) An empirical model of total solar irradiance variation between 1874 and 1988. Science 247:556–558. doi:10.1126/science.247.4942.556 CrossRefGoogle Scholar
  11. Foukal P, Fröhlich C, Spruit H, Wigley TML (2006) Variations in solar luminosity and their effect on the earth’s climate. Nature 443:161–166. doi:10.1038/nature05072 CrossRefGoogle Scholar
  12. Fröhlich C (2004) Solar irradiance variability, in geophysical monograph 141: solar variability and its effect on climate. AGU, Washington, pp. 97–110. Chap. 2: Solar energy flux variationsGoogle Scholar
  13. Fröhlich C (2005) Solar irradiance variability since 1978. Memorie della Societa Astronomica Italiana 76:731–734Google Scholar
  14. Fröhlich C (2006a) Solar irradiance variability since 1978: revision of the PMOD composite during solar cycle 21. Space Sci Rev 125:53–65. doi:10.1007/s11214-006-9046-5 CrossRefGoogle Scholar
  15. Fröhlich C (2006b) Total solar irradiance variability: what have we learned from SOHO/VIRGO about solar cycle 23?. In: H. Lacoste (ed) Proceedings of SOHO 17: 10 Years of SOHO and Beyond, Giardini Naxos, Sicily, Italy, 7–12 May 2006 (ESA SP-217). ESA Publication Division, ESTEC, 2200 AG, The Netherlands, p36_froh. Also available from
  16. Fröhlich C (2009) Evidence of a long-term trend in total solar irradiance. Astron Astrophys 501:27–30. doi:10.1051/0004-6361/200912318 CrossRefGoogle Scholar
  17. Fröhlich C (2010) Possible influence of aperture heating on VIRGO radiometry on SOHO. AGU Fall Meeting Abstracts, B874Google Scholar
  18. Fröhlich C (2010) Solar radiometry, in observing photons in space. In: Huber MCE, Culhane JL, Pauluhn A, Timothy JG, Wilhelm K, Zehnder A (eds) ISSI Scientific Reports SR-009. ESA Communications, Noordwijk pp 525–540. Chap. 32Google Scholar
  19. Fröhlich C (2011c) Total solar irradiance: what have we learned from the last three cycles and the recent minimum? Space Sci Rev 158. published online 11 May 2011. doi:10.1007/s11214-011-9780-1
  20. Fröhlich C (2012) Spectral irradiance variation during cycle 23 from the three-channel VIRGO/SPM. Some preliminary results were presented at the SORCE meeting: (in preparation)
  21. Fröhlich C, Lean J (1998) Total solar irradiance variations: the construction of a composite and its comparison with models. In: Deubner FL, Christensen-Dalsgaard J, Kurtz D (eds) IAU symposium 185: new eyes to see inside the sun and stars. Kluwer, Dordrecht, pp 89–102CrossRefGoogle Scholar
  22. Fröhlich C, Lean J (2004) Solar radiative output and its variability: evidence and mechanisms. Astron Astrophys Rev 12:273–320. doi:10.1007/s00159-004-0024-1 CrossRefGoogle Scholar
  23. Fröhlich C, Crommelynck D, Wehrli C, Anklin M, Dewitte S, Fichot A, Finsterle W, Jiménez A, Chevalier A, Roth HJ (1997) In-flight performances of VIRGO solar irradiance instruments on SOHO. Sol Phys 175:267–286. doi:10.1023/A:1004929108864 CrossRefGoogle Scholar
  24. Fröhlich C, Appourchaux T, Chaplin WJ, Elsworth Y, Wachter R (2006) Solar cycle variability of total solar irradiance and P-mode frequencies, in SOHO-17. 10 years of SOHO and beyond. presented, but unpublished poster available from
  25. Fröhlich C (2011a) A four-component proxy model for total solar irradiance calibrated during solar cycles 21–23. Contrib Astron Obs Skalnate Pleso 41:113–132Google Scholar
  26. Fröhlich C (2011b) Total solar irradiance during the last three cycles and what it means for the reconstruction back to 1915. EGU Abstracts,CL2.12. available from; a detailed publication is in preparation
  27. Hagenaar HJ, Schrijver CJ, Title AM (2003) The properties of small magnetic regions on the solar surface and the implications for the solar dynamo(s). Astrophys J 584:1107–1119. doi:10.1086/345792 CrossRefGoogle Scholar
  28. Hoyt DV, Kyle HL, Hickey JR, Maschhoff RH (1992) The NIMBUS-7 solar total irradiance: a new algorithm for its derivation. J Geophys Res 97:51–63CrossRefGoogle Scholar
  29. Hudson HS (1988) Observed variability of the solar luminosity. Ann Rev Astron Astrphys 26:473–508. doi:10.1146/annurev.aa.26.090188.002353 CrossRefGoogle Scholar
  30. Kopp G, Lean JL (2011) A new, lower value of total solar irradiance: evidence and climate significance. Geophys Res Lett 38:L01706. doi:10.1029/2010GL045777 CrossRefGoogle Scholar
  31. Kopp G, Lawrence G, Rottman G (2005) The total irradiance monitor (TIM): science results. Sol Phys 230:129–139. doi:10.1007/s11207-005-7433-9 CrossRefGoogle Scholar
  32. Kopp G, Heuerman K, Harber D, Drake G (2007) The tsi radiometer facility: absolute calibrations for total solar irradiance instruments. In Society of photo-optical instrumentation engineers (SPIE) conference series 6677: 667709 doi:10.1117/12.734553
  33. Krivova NA, Solanki SK, Schmutz W (2011) Solar total irradiance in cycle 23. Astron Astrophys 529:A81. doi:10.1051/0004-6361/201016234 CrossRefGoogle Scholar
  34. Krivova NA, Solanki SK, Fligge M, Unruh YC (2003) Reconstruction of solar total and spectral irradiance variations in cycle 23: is solar surface magnetism the cause?. Astron Astrophys 399:1–4CrossRefGoogle Scholar
  35. Kuhn JR, Libbrecht KG (1991) Nonfacular solar luminosity variations. Astrophys J 381:35–37CrossRefGoogle Scholar
  36. Kuhn JR, Libbrecht KG, Dicke R (1988) The surface temperature of the sun and changes in the solar constant. Science 242:908–911Google Scholar
  37. Lee RB III, Barkstrom BR, Cess RD (1987) Characteristics of the earth radiation budget experiment solar monitors. Appl Opt 26:3090–3096CrossRefGoogle Scholar
  38. Lee RB III, Gibson MA, Wilson RS, Thomas S (1995) Long-term total solar irradiance variability during sunspot cycle 22. J Geophys Res 100:1667–1675. doi:10.1029/94JA02897 CrossRefGoogle Scholar
  39. Livingston W, Wallace L, White OR, Giampapa MS (2007) Sun-as-a-star spectrum variations 1974–2006. Astrophys J 657:1137–1149. doi:10.1086/511127 CrossRefGoogle Scholar
  40. Mekaoui S, Dewitte S, Conscience C, Chevalier A (2010) Total solar irradiance absolute level from DIARAD/SOVIM on the international space station. Adv Space Res 45:1393–1406. doi:10.1016/j.asr.2010.02.014 CrossRefGoogle Scholar
  41. Ortiz A, Domingo V, Sanahuja B (2006) The intensity contrast of solar photospheric faculae and network elements. II. Evolution over the rising phase of solar cycle 23. Astron Astrophys 452:311–319. doi:10.1051/0004-6361:20053869 CrossRefGoogle Scholar
  42. Penn MJ, Livingston W (2006) Temporal changes in sunspot umbral magnetic fields and temperatures. Astrophys J 649:45–48. doi:10.1086/508345 CrossRefGoogle Scholar
  43. Pietarila Graham J, Danilovic S, Schüssler M (2009) Turbulent magnetic fields in the quiet sun: implications of hinode observations and small-scale dynamo simulations. Astrophys J 693:1728–1735. doi:10.1088/0004-637X/693/2/1728 CrossRefGoogle Scholar
  44. Scafetta N (2010) Climate change and its causes, a discussion about some key issues, in SPPI Original Paper (Science and Public Policy Institute, Haymarket, Va 20169, USA), pp 1–56.
  45. Scafetta N, Willson RC (2009) ACRIM-gap and TSI trend issue resolved using a surface magnetic flux TSI proxy model. Geophys Res Lett 36:L05701. doi:10.1029/2008GL036307 CrossRefGoogle Scholar
  46. Schnerr RS, Spruit HC (2011) The total solar irradiance and small scale magnetic fields. In: Kuhn JR, Harrington DM, Lin H, Berdyugina SV, Trujillo-Bueno J, Keil SL, Rimmele T (eds) Astronomical society of the Pacific conference series, vol 437, pp 167–175Google Scholar
  47. Shapiro AI, Schmutz W, Rozanov E, Schoell M, Haberreiter M, Shapiro AV, Nyeki S (2011) A new approach to the long-term reconstruction of the solar irradiance leads to large historical solar forcing. Astron Astrophys 529:A67. doi:10.1051/0004-6361/201016173 CrossRefGoogle Scholar
  48. Solanki SK, Krivova NA, Wenzler T (2005) Irradiance models. Adv Space Res 35:376–383. doi:10.1016/j.asr.2004.12.077 CrossRefGoogle Scholar
  49. Steinhilber F (2010) Total solar irradiance since 1996: is there a long-term variation unrelated to solar surface magnetic phenomena? Astron Astrophys 523:A39. doi:10.1051/0004-6361/200811446 CrossRefGoogle Scholar
  50. Steinhilber F, Beer J, Fröhlich C (2009) Total solar irradiance during the holocene. Geophys Res Lett 36:L19704. doi:10.1029/2009GL040142 CrossRefGoogle Scholar
  51. Tapping KF, Boteler D, Charbonneau P, Crouch A, Manson A, Paquette H (2007) Solar magnetic activity and total irradiance since the maunder minimum. Sol Phys 246:309–326. doi:10.1007/s11207-007-9047-x CrossRefGoogle Scholar
  52. Thuillier G, Dewitte S, Schmutz W (2011) Picard team, the sun-climate connection through measurements and modeling: the Picard investigation. In: Miralles MP, Sánchez Almeida J (eds) The sun, the solar wind, and the heliosphere. IAGA Special Sopron Book Series, Springer, Berlin, pp 365Google Scholar
  53. Unruh YC, Solanki SK, Fligge M (1999) The spectral dependence of facular contrast and solar irradiance variations. Astron Astrophys 345:635–642Google Scholar
  54. Viereck RA, Snow M, Deland MT, Weber M, Puga L, Bouwer D (2010) Trends in solar UV and EUV irradiance: an update to the MgII Index and a comparison of proxies and data to evaluate trends of the last 11-year solar cycle. AGU Fall Meeting Abstracts: Poster GC21B-0877Google Scholar
  55. Vögler A, Schüssler M (2007) A solar surface dynamo. Astron Astrophys 465:43–46. doi:10.1051/0004-6361:20077253 CrossRefGoogle Scholar
  56. Wenzler T, Solanki SK, Krivova NA, Fluri DM (2004) Comparison between KPVT/SPM and SoHO/MDI magnetograms with an application to solar irradiance reconstructions. Astron Astrophys 427:1031–1043. doi:10.1051/0004-6361:20041313 CrossRefGoogle Scholar
  57. Willson RC (1984) Measurements of solar total irradiance and its variability. Space Sci Rev 38:203–242. doi:10.1007/BF00176830 CrossRefGoogle Scholar
  58. Willson RC (1994) Irradiance Observations from SMM, UARS and ATLAS Experiments. In: Pap J, Fröhlich C, Hudson HS, Solanki S (eds) IAU Colloquium No. 143: the sun as a variable star: solar and stellar irradiance variations. Cambridge University Press, Cambridge, pp 54–62Google Scholar
  59. Willson RC (1997) Total solar irradiance trend during solar cycles 21 and 22. Science 277: 1963–1965. see also comment by R. Kerr on page 1923 of the same issue of Science. doi:10.1126/science.277.5334.1963
  60. Willson RC (2001) The ACRIMSAT/ACRIM III experiment: extending the precision, long-term total solar irradiance climate database. Earth Observer 13:14–17Google Scholar
  61. Willson RC (2011) ACRIM3 and ACRIM composite results after 2010 Reflect LASP/TRF determined scattering, diffraction and basic scale calibration adjustments. Data available from and
  62. Willson RC, Hudson HS (1991) The Sun’s luminosity over a complete solar cycle. Nature 351:42–44. doi:10.1038/351042a0 CrossRefGoogle Scholar
  63. Willson RC, Mordvinov AV (2003) Secular total solar irradiance trend during solar cycles 21-23. Geophys Res Lett 30:1199. doi:10.1029/2002GL016038 CrossRefGoogle Scholar
  64. Woods TN, Tobiska WK, Rottman GJ, Worden JR (2000) Improved solar Lyman α irradiance modeling from 1947 through 1999 based on UARS observations. J Geophys Res 105:27195–27216. doi:10.1029/2000JA000051 CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.Physikalisch-Meteorologisches Observatorium Davos, World Radiation CenterDavos DorfSwitzerland

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