The Prad of the surface photon stream on the atmosphere was 0.575 μPa. (wattsupwiththat.com)
In the traditional view of photosynthesis, the energy carried by photons streaming from the sun is transferred by bouncing from one chlorophyll molecule to the next, a process that ultimately builds simple carbohydrates from water and carbon dioxide. (discovermagazine.com)
The solar photon stream changes with latitude and responds also to the solar activity. (scienceofdoom.com)