radiant fluence rate
mean value of irradiance on the outer curved surface of a very small (real or imaginary) sphere at a point in space
Note 1 to entry: The spherical irradiance can be expressed by
Note 2 to entry: The spherical irradiance is the quotient of the radiant flux of all the radiation incident on the outer surface of an infinitely small sphere centred at the specified point and the area of the diametrical cross-section of that sphere.
Note 3 to entry: The analogous quantities "spherical illuminance",
Note 4 to entry: The spherical irradiance is the appropriate radiometric quantity for describing a dose rate for a photobiological or photochemical effect in a scattering medium (e.g. light in skin). The spherical irradiance is also the appropriate quantity for describing the irradiation of microorganisms. The spherical irradiance is frequently used incorrectly as a substitute for irradiance in some publications.
Note 5 to entry: The spherical irradiance is expressed in watt per square metre (W⋅m−2).
Note 6 to entry: This entry was numbered 845-01-40 in IEC 60050-845:1987.
Note 7 to entry: This entry was numbered 17-1245, 17-455 and 17-1024 in CIE S 017:2011.