The radiant power (energy per unit time) that falls on a detector per unit surface area of the detector per unit bandwidth of the radiation. It thus measures both the spatial (surface) density and a spectral density of the flux received from an astronomical source. Flux density in radio astronomy is...
<radiobiology> Total amount of a quantity passing through a unit surface area in unit time ... See: flux. ... (09 Oct 1997) ... 
The amount of energy or matter passing through a unit area perpendicular to the stream per unit time.
Type: Term Definitions: 1. either particle flux density, the particle fluence rate, or energy flux density, the energy fluence rate of intensity. Synonyms: flux5
[n] - (physics) the number of flux changes per unit area
flux noun (physics) the number of changes in energy flow across a given surface per unit area
the magnetic, radiant, or electric flux per unit of cross-sectional area.