Volume 27, Issue 16 p. 2425-2428
Free Access

Evolution of the Sun's Spectral Irradiance Since the Maunder Minimum

Judith Lean

Judith Lean

E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC

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First published: 15 August 2000


Because of the dependence of the Sun's irradiance on solar activity, reductions from contemporary levels are expected during the seventeenth century Maunder Minimum. New reconstructions of spectral irradiance are developed since 1600 with absolute scales traceable to space-based observations. The long-term variations track the envelope of group sunspot numbers and have amplitudes consistent with the range of Ca II brightness in Sun-like stars. Estimated increases since 1675 are 0.7%, 0.2% and 0.07% in broad ultraviolet, visible/near infrared and infrared spectral bands, with a total irradiance increase of 0.2%.