Starfish Prime: The First Accidental Geomagnetic Storm

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July 9, 2022: 

Sixty years ago today, one of the biggest geomagnetic storms of the Space Age struck Earth. It didn’t come from the sun.

„We made it ourselves, “recalls Clive Dyer of the University of Surrey Space Centre in Guildford UK. „It was the first anthropogenic space weather event. “

On July 9, 1962, the US military exploded a thermonuclear warhead 250 miles above the Pacific Ocean–a test called „Starfish Prime. “What happened next surprised everyone. Witnesses from Hawaii to New Zealand reported auroras dancing overhead, magnificent midnight „rainbow stripes“ that tropical sky watchers had never seen before. Radios fell silent, then suddenly became noisy, as streetlights went dark in Honolulu.

Above: ‘Nuclear auroras’ viewed from Honolulu (left) and from a surveillance aircraft (right) on July 9, 1962.

Starfish Prime essentially created an artificial solar storm complete with auroras, geomagnetic activity, and blackouts. Much of the chaos that night was caused by the electromagnetic pulse (EMP)–a ferocious burst of radiation that ionized the upper atmosphere. Ionized air over the Pacific pinned down Earth’s magnetic field, then let it go again when the ionization subsided. The rebound created a manmade geomagnetic storm for hundreds of miles around the blast zone.

Dyer, who is widely known for his studies of extreme space weather events, was still in school when the bomb exploded. „In 1962 the Cold War was red hot, and we all thought the end was nigh, “he says. „Starfish Prime was a defining event. “

„The explosion led to the early demise of all the spacecraft in orbit at the time. These included Ariel-1, the UK’s first spacecraft, and Telstar-1, a US communications satellite which had the bad luck to be launched the very next day. “

Credit: R.E. Fischell, “ANNA-1B Solar Cell Damage Experiment,” Transcript of the Photovoltaic Specialists Conference, April 10, 1963, Washington DC.

Normally, geomagnetic storms bring down satellites via orbital decay. The upper atmosphere heats up and expands to the point where it can pull satellites down toward Earth. Starfish Prime was different.

„The explosion filled Earth’s magnetosphere with energetic electrons, “explains Dyer. „Electrons were injected by the gradual beta decay of fission products and added to our planet’s natural radiation belts. There were increased fluxes of trapped electrons for many years after the blast. “

These artificial electrons hit satellites hard, degrading their electronics and solar arrays.

„Ariel-1 became almost unusable after 4 days due to power degradation and tape recorder failure, “recalls Dyer. „The Telstar satellite lasted until November 1962 when its command decoder failed. It still managed to provide the first transatlantic TV feed, synchronize UK/US time to 1 microsecond and inspired the Tornado’s rock classic ‚Telstar, ‘which used recordings of a flushing toilet played backwards. “

Starfish Prime serves as a warning of what could happen if Earth is blasted by high doses of radiation. Sixty years later, researchers are still learning what it can teach us about the vulnerability of power grids. An even scarier atmospheric explosion may have been Soviet test 184 (also designated K3) on October 22, 1962, which set fires and knocked out hundreds of miles of power lines in Kazakhstan. That, however, is a different anniversary.


July 8, 2022