Chapman equation

Chapman equation

[′chap·mən i‚kwā·zhən] (geophysics) A theoretical relation describing the distribution of electron density with height in the upper atmosphere. (statistical mechanics) The relationship that the viscosity of a gas equals (0.499) mv /[√2 πσ2(1 + C/T)], where m is the mass of a molecule, v its average speed, σ its collision diameter, C the Sutherland constant, and T the absolute temperature (Kelvin scale).