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Chapman, Sydney

theory atmosphere gases thermal

(1888–1970) British applied mathematician: developed the kinetic theory of gases and worked on gaseous thermal diffusion, geomagnetism, tidal theory and the atmosphere.

Chapman studied engineering at Manchester and mathematics at Cambridge, graduating in 1910. During his career he held professorships in Manchester, London and Oxford, and from 1954 worked at the High Altitude Observatory, Boulder, CO, and the Geophysical Institute in Alaska.

Chapman’s interests were broad. He made a notable contribution to the kinetic theory of gases, taking the theory beyond the earlier work of and to the Chapman–Enskog theory of gases.

Thermal diffusion refers to heat transfer between two parts of a solid, liquid or gas that are at different temperatures, in the absence of convection. He applied his theory to a variety of problems, notably in the upper atmosphere. (Later, isotopes for atomic fission were separated by use of gaseous thermal diffusion.) On geomagnetism, his other main interest, he investigated why the Earth’s magnetic field varies with periods equal to the lunar day (27.3 days) and its submultiples; he showed this was due to a tidal movement in the Earth’s atmosphere due to the Moon. The Chapman–Ferraro theory of magnetic storms predated modern plasma theory. He also studied the formation of ozone in the atmosphere and the ionizing effect of solar ultraviolet light on the ionosphere (the Chapman layer being named for him). In his later years he developed, with S I Akasofu (1930– ), the modern theory of geomagnetic storms, the ring current and the aurora.

Chappell Co. [next] [back] Chapman, George (1559–1631) - BIOGRAPHY, CRITICAL RECEPTION

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