An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The → energy at all → wavelengths that is incident on unit area of surface in unit time. It is measured in Watts per square meter.

Irradiance, from ir- variant of → in- (by assimilation) before r + radi(ant), → radiation, + -ance a suffix used to form nouns either from adjectives in -ant or from verbs.

Tâbešdâri, from tâbeš, → radiation, + dâri, verbal noun from dâštan "to have, hold," → property.

The radiative power per unit area in all wavelengths from the Sun received by the Earth at its average distance from the Sun. Its mean value is called the → solar constant. The solar irradiance changes over a year by about 6.6% due to the variation in the Earth/Sun distance. Moreover, solar activity variations cause irradiance changes of up to 1%.

→ solar; → irradiance.