A unit of luminous flux used to measure air glow, for example of aurora, first proposed in 1956.¹ Symbol, R. The SI prefixes are used with this unit. One rayleigh is 10¹⁰/4π quanta per square meter per second per steradian.
The night sky has a luminous intensity of about 250 rayleigh, while auroras can reach values of 1000 kilorayleigh.
The unit is named for Robert John Strutt, fourth Lord Rayleigh (1875 – 1947).
1. D. M. Hunter, F. E. Roach, and J. W. Chamberlaine.
Journal of Atmospheric and Terrestrial Physics (GB) vol. 8, no. 6, page 345 (1956).
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Last revised: 8 September 2005.