The English geophysicist Sydney Chapman (1888-1970) made fundamental contributions to gas theory, to analysis of geomagnetic variations and atmospheric tides, and to theories of magnetic storms, auroras, and ionospheric layers.
Sydney Chapman was born at Eccles near Manchester on Jan. 29, 1888. Winning university scholarships, he first took an engineering degree at Manchester (1907), then mathematics degrees at Manchester (1908) and Cambridge (1911).
Chapman began work on gas theory during his third year at Cambridge, and he continued this work when he returned to Cambridge in 1914, producing two trailblazing papers. He shared with David Enskog the credit for a new method of investigating transport phenomena in gases and the discovery of gaseous thermal diffusion. Gas theory provided the background for much of his later work.
Chapman's years at the Greenwich Observatory, where he became a chief assistant under Frank Dyson (astronomer royal) in 1911, largely determined his future bent. He began by supervising the reconstruction of the magnetic observatory. Finding that magneticians had been far readier to accumulate data than to interpret them, he set about to analyze geomagnetic variations. Since one type of systematic variation appeared to arise from a very small lunar tide in the ionosphere, he sought and found a lunar tide in the barometric records and with immense labor, extending over 30 years, determined its properties over the globe. He devised methods of data handling, now commonplace but then almost unknown.
In 1931 he published two classic papers on the formation of the ionosphere by radiation from the sun, describing the standard "Chapman layer." Other papers on the upper-atmosphere photochemistry followed.
Dyson at Greenwich drew Chapman's attention to the apparent connection between magnetic storms and solar flares, so setting in motion a further series of investigations, which continued for 50 years. The highlight of the results was the Chapman-Ferraro theory of magnetic storms (1930-1933), explaining the storms by the interaction of ionized solar streams with the geomagnetic field. The theory was correct but incomplete; only after the discovery of the Van Allen radiation belts could it be completed.
Chapman was professor of mathematics at Manchester (1919-1924), at the Imperial College (1924-1946), and at Oxford (1946-1953). Retiring from Oxford, he took posts at College, Alaska, at Boulder, Colo., and elsewhere. In 1957 he produced a paper on the sun's corona, foreshadowing the discovery of the solar wind, and began a series of papers on auroras. He presided over the special committee that organized the International Geophysical Year of 1957-1958, which owed an immense amount to his unflagging efforts and inspiration. He died on June 16, 1970.
Syun-Ichi Akasofu, Benson Fogle, and Bernhard Haurwitz, eds., Sydney Chapman, Eighty: From His Friends (1968), contains a large number of anecdotes about Chapman together with autobiographical notes covering the years up to about 1930. T. G. Cowling wrote a biographical note on Chapman for publication in Biographical Memoirs of Fellows of the Royal Society (1971).
Alton, Jeannine, Report on the papers of Professor Sydney Chapman, FRS (1888-1970): deposited in the Bodleian Library, Oxford: with memorandum on the location of other papers, London: Reproduced for the Contemporary Scientific Archives Centre by the Royal Commission on Historical Manuscripts, 1974.