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Long-term variations in total solar irradianceFor more than a decade total solar irradiance has been monitored simultaneously from space by different satellites. The detection of total solar irradiance variations by satellite-based experiments during the past decade and a half has stimulated modeling efforts to help identify their causes and to provide estimates of irradiance data, using `proxy' indicators of solar activity, for time intervals when no satellite observations exist. In this paper total solar irradiance observed by the Nimbus-7/Earth Radiation Budget (ERB), Solar Maximum Mission (SMM)/Active Cavity Radiometer Irradiance Monitor (ACRIM) 1, and Upper Atmosphere Research Satellite (UARS)/ACRIM 2 radiometers is modeled with the Photometric Sunspot Index and the Mg II core-to-wing ratio. Since the formation of the Mg II line is very similar to that of the Ca II K line, the Mg core-to-wing ratio, derived from the irradiance observations of the Nimbus-7 and NOAA9 satellites, is used as a proxy for the bright magnetic elements. It is shown that the observed changes in solar irradiance are underestimated by the proxy models at the time of maximum and during the beginning of the declining portion of solar cycle 22 similar to behavior just before the maximum of solar cycle 21. This disagreement between total irradiance observations and their model estimates is indicative of the fact that the underlying physical mechanism of the changes observed in the solar radiative output is not well-understood. Furthermore, the uncertainties in the proxy data used for irradiance modeling and the resulting limitation of the models should be taken into account, especially when the irradiance models are used for climatic studies.
Document ID
19950046571
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Pap, Judit M.
(Jet Propulsion Lab. Pasadena, CA, US, United States)
Willson, Richard C.
(Jet Propulsion Lab. Pasadena, CA, US, United States)
Froelich, Claus
(Physikalisch-Meteorologisches Observatorium Davos Davos Dorf, Switzerland)
Donnelly, Richard F.
(National Oceanic and Atmospheric Administration, Boulder, CO US, United States)
Puga, Larry
(National Oceanic and Atmospheric Administration, Boulder, CO US, United States)
Date Acquired
August 16, 2013
Publication Date
June 1, 1994
Publication Information
Publication: Solar Physics
Volume: 152
Issue: 1
ISSN: 0038-0938
Subject Category
Solar Physics
Accession Number
95A78170
Distribution Limits
Public
Copyright
Other

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