energy flux

{{short description|Rate of transfer of energy through a surface}}

Energy flux is the rate of transfer of energy through a surface. The quantity is defined in two different ways, depending on the context:

1. Total rate of energy transfer (not per unit area);{{cite web|url=http://hesperia.gsfc.nasa.gov/sftheory/glossary.htm|title=Solar Physics Glossary|publisher=Nasa|accessdate=2008-12-24}} SI units: W = J⋅s⁻¹.
2. Specific rate of energy transfer (total normalized per unit area); {{cite web|url=http://en.mimi.hu/astronomy/energy_flux.html|title=Energy flux|accessdate=2008-12-24}} SI units: W⋅m⁻² = J⋅m⁻²⋅s⁻¹:
3. * This is a vector quantity, its components being determined in terms of the normal (perpendicular) direction to the surface of measurement.
4. * This is sometimes called energy flux density, to distinguish it from the first definition.
5. * Radiative flux, heat flux, and sound energy flux densityhttps://www.acoustic-glossary.co.uk/sound-energy.htm (also sound intensity)https://www.acoustic-glossary.co.uk/sound-intensity.htm are specific cases of this meaning.