Chapman, Sydney

Born Jan. 29, 1888, in Eccles, Lancashire; died June 16, 1970. British mathematician, physicist, and geophysicist. Fellow of the Royal Society of London (1919).

Chapman graduated from the University of Manchester in 1907 and from Cambridge University in 1911. He was a professor at the University of Manchester from 1919 to 1924, at the Imperial College of Science and Technology from 1924 to 1946, and at Oxford University from 1946 to 1953. He served as president of the London Mathematical Society from 1929 to 1931, of the Royal Meteorological Society from 1932 to 1934, and of the International Association of Meteorology and Atmospheric Physics from 1936 to 1948. From 1953 to 1959 he was president-of the central organizing committee for the International Geophysical Year.

Chapman’s principal works deal with the kinetic theory of gases, terrestrial magnetism, the investigation of the ionosphere and the upper atmosphere, atmospheric electricity, and mathematics. In 1919 he developed the dynamo theory of lunar daily variations of the geomagnetic field (the theory of drift currents). In 1930 he proposed a new photochemical theory of the formation of ozone, and in 1931 he set forth a theory of the formation of the electron-concentration layers of the ionosphere. Chapman developed a theory of the particle fluxes continuously emitted by the sun. With V. Ferrara, he used this theory in 1931 and 1932 to construct a theory of geomagnetic storms and of auroras. He studied airglow and investigated the influence of the X-radiation of auroras on the ionization of the lower ionosphere layers that leads to absorption of radio waves.

In 1957, Chapman analyzed the extent of the solar corona and investigated the influence of the corpuscular radiation of the sun on the thermal conditions of the earth’s atmosphere. He made an important contribution to the development of the kinetic theory of gases. He proposed methods of solving the Boltzmann transport, or kinetic, equation. Chapman gave a theoretical demonstration, independently of the Swedish scientist D. Enskog, of thermal diffusion in gases and subsequently, with F. Dootsen, found experimental confirmation of such diffusion.