On May 23, 1967, … all three of the United States’ ballistic missile early-warning radars became simultaneously jammed. Located in the high-latitude areas of Alaska, Greenland, and the United Kingdom, these radars were designed to detect incoming Soviet missiles, and any attack or disruption of these radars were considered to be an act of war.
The United States Air Force, believing their radars had been intentionally jammed by the Soviet Union, authorized aircraft with nuclear-strike capabilities to take to the skies. Timely information from space-weather forecasters, who realized that it was a powerful solar flare jamming the radar, managed to prevent military action just in time.
Just a few days earlier, an unusually large group of sunspots — cooler surface regions on the Sun associated with stronger solar magnetic fields — had rotated into Earth’s view. … Observers documented a large solar flare erupting from the solar surface at 18:40 UT (2:40 p.m. EDT): a burst of powerful radio waves and X-rays was headed straight for Earth. …
Unaware of the solar activity, outside agencies and officials at the highest levels of the U.S. government put nuclear fighter jets on high alert, even as the Air Force’s Air Weather Service (AWS) was notifying the North American Air Defense Command (NORAD) of the solar activity. Stationed at NORAD on the day of the solar flare was now-retired colonel Arnold L. Snyder, who recalls coordinating with a tropospheric weather forecaster also working at NORAD during the day of the event: “I specifically recall responding with excitement [to the atmospheric weather forecaster], ‘Yes, half the sun has blown away!’ and then related the event details in a calmer, more quantitative way.”
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