energy density

Energy density is the amount of energy stored in a given (unit) volume, e.g., J/m³ (joules per meter cubed). The concept is used in engineering (e.g., batteries) and science, including astrophysics. One use is in radiative transfer models, using density of energy of the electromagnetic radiation passing through a volume at a given time as a term in formulae. Another use is for the energy inherent in magnetic fields.