Academic journal article Proceedings of the American Philosophical Society

John Paul Wild

Academic journal article Proceedings of the American Philosophical Society

John Paul Wild

Article excerpt

17 MAY 1923 * 10 MAY 2008

John Paul Wild was born in Sheffield, England, the son of a cutlery manufacturer who lost everything in the Great Depression. Paul's father went to the U.S. when Paul was three months old and, although he was able to provide support after selling some patents, Paul did not see him for the next thirty-three years. Paul had an early love of mathematics that he attributed to the enthusiasm and encouragement of his school mathematics teachers. He went to Cambridge University in 1942 and studied mathematics and physics before joining the navy in July 1943. This two years was to be his only period of university study.

Paul served as a radar officer on the flagship HMS King George V in the British Pacific Fleet for two and a half years. On one of the many visits the fleet made to Sydney, Australia, Paul met Elaine Hull, and their friendship grew with subsequent visits. Paul returned to England after the war and taught radar to naval officers, corresponding frequently with Elaine. In 1947, he obtained a job at the Radiophysics Laboratory of Australia's Council for Scientific and Industrial Research (CSIR) and moved to Sydney, his proposal of marriage by mail having already been accepted. Paul's first role was the relatively mundane maintenance and development of test equipment, but after a year he was able to join Joe Pawsey's radioastronomy group. Paul was a great admirer of Pawsey, who provided "an ideal environment to allow everyone to use their own initiative." CSIR became the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in 1949.

Paul worked with Lindsay McCready to build, at Pawsey's suggestion, the first spectrograph to study the frequency dependence of solar bursts. This instrument provided a display of frequency versus time covering a swept frequency range from 40 to 70 MHz. Paul travelled to Penrith, 50 km west of Sydney, by train each day with a technician and a hand-cranked movie camera to record the cathode ray screen showing the variation of intensity with frequency of the solar radio emission. Paul recalled, "Every now and then a great burst would come from the sun and we were very excited and we photographed everything that went on. . . . After four months we got so much data that we just closed everything down and came back and I analysed the data at very great length; the results were spectacular."

Three types of bursts were identified - which they named Types I, II, and III - distinguished by the way the frequency changed with time. In a series of papers published in 1950, they presented their data and the conclusion that Type II bursts were associated with shock waves coming out through the solar atmosphere at 1,000 km/sec that were associated, about a day later, with aurorae visible near the earth's poles. The more frequent Type III bursts were associated with streams of electrons being ejected one hundred times faster - at a third the speed of light - and taking only an hour to reach the earth. This was one of the first realisations that astrophysical phenomena could result in the production of particles travelling at relati vistic speeds. The interpretations proved to be correct, and their naming of the burst types became the standard.

The success of these observations led to the construction of three rhombic spectrograph antennas at Dapto, 100 km south of Sydney, to conduct further studies of the sun at frequencies between 40 and 240 MHz, which confirmed and extended the Penrith work. Paul likened this research to the study of taxonomy that preceded Darwin's Origin of Species. His analysis of the anatomy of the solar flares and his development of the physical interpretation culminated in a unified model that integrated the apparently complex radio flare phenomena in the solar chromosphere, in the solar corona, and in the interplanetary space.

In the course of this solar work, Paul became interested in the radio spectrum of hydrogen and wrote up an internal report related to the potential for spectral lines in the solar bursts. …

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