James Stanley Hey Discovers Solar Radio Waves

Context

During the Second World War, Britain relied heavily on radar systems to detect and counter Luftwaffe air raids, with chains of stations providing early warning along the coast and supporting anti-aircraft defenses. German forces had begun deliberate jamming of these radars, as demonstrated during the February 1942 escape of the Scharnhorst and Gneisenau through the English Channel, prompting urgent efforts to develop countermeasures. James Stanley Hey, a physicist who had joined the Air Defence Research and Development Establishment's operational research group in 1940 after teaching at Burnley Grammar School, was assigned specifically to investigate jamming problems from his base near Richmond Park in Surrey.

What Happened

On 27 and 28 February 1942, radar operators at multiple anti-aircraft sites across southern England reported intense, persistent interference on wavelengths between 4 and 8 metres that overwhelmed normal signals. Hey examined the pattern of reports and noticed that the direction of strongest noise shifted in precise alignment with the Sun's position in the sky rather than any fixed terrestrial source or enemy transmitter. He contacted astronomers at the Royal Observatory, Greenwich, who confirmed that a large and highly active sunspot group was crossing the solar disk at the time, providing the physical link between the observed radio noise and solar activity.

Aftermath

Hey quickly concluded that the sunspot region, with its intense magnetic fields, was generating metre-wave radio emissions, marking the first identification of a specific astronomical radio source. The finding remained classified for the duration of the war, with no immediate publication or public announcement, though an independent confirmation at centimetre wavelengths was made later in 1942 by American physicist George Clark Southworth.

Legacy

Hey's accidental discovery established solar radio astronomy as a viable discipline and demonstrated how wartime radar technology could be repurposed for fundamental science once security restrictions lifted after 1945. It paved the way for systematic studies of solar flares, coronal mass ejections, and their effects on space weather, while Hey's subsequent work at Richmond Park influenced the founding of major radio observatories led by Bernard Lovell at Jodrell Bank and Martin Ryle at Cambridge.