Editing Sunlight (section)

===Solar constant===

[[File:Solar irradiance spectrum 1992.gif|thumb|upright=1.3|Solar irradiance spectrum at top of atmosphere, on a linear scale and plotted against [[wavenumber]]]]
{{Main|Solar constant}}

The '''solar constant''' is a measure of [[flux density]], is the amount of incoming solar [[electromagnetic radiation]] per unit area that would be incident on a plane perpendicular to the rays, at a distance of one [[astronomical unit]] (AU) (roughly the mean distance from the Sun to Earth). The "solar constant" includes all types of solar radiation, not just the [[visible light]]. Its average value was thought to be approximately 1,366&nbsp;W/m<sup>2</sup>,<ref name=TSI20>{{cite web |url=http://acrim.com/TSI%20Monitoring.htm |title=Satellite observations of total solar irradiance |publisher=Acrim.com |access-date=2012-02-12 |url-status=live |archive-url=https://web.archive.org/web/20030204191816/http://acrim.com/TSI%20Monitoring.htm |archive-date=2003-02-04 }}</ref> varying slightly with [[solar cycle|solar activity]], but recent recalibrations of the relevant satellite observations indicate a value closer to 1,361&nbsp;W/m<sup>2</sup> is more realistic.<ref name=KoppLean11>{{cite journal|last1=G. Kopp|author2=J. Lean |title=A new, lower value of total solar irradiance: Evidence and climate significance|journal=Geophys. Res. Lett.|date=2011|pages=L01706|doi=10.1029/2010GL045777|bibcode = 2011GeoRL..38.1706K|first1=Greg|volume=38 |issue=1 |doi-access=free}}</ref>