A solar storm that jammed America's radar and radio communications at the height of the Cold War could have led to a disastrous military conflict with the Soviet Union, if not for the US Air Force's budding efforts to monitor the Sun's activity, a new study has found.
On May 23, 1967, the US Air Force prepared aircraft for war, thinking the country's surveillance radars in polar regions were being jammed by the Soviet Union.
Just in time, military space weather forecasters conveyed information about the solar storm's potential to disrupt radar and radio communications.
The planes remained on the ground and the US avoided a potential nuclear weapon exchange with the Soviet Union, researchers said.
"Had it not been for the fact that we had invested very early on in solar and geomagnetic storm observations and forecasting, the impact (of the storm) likely would have been much greater," said Delores Knipp, a space physicist at the University of Colorado in Boulder.
The US military began monitoring solar activity and space weather - disturbances in Earth's magnetic field and upper atmosphere - in the late 1950s.
In the 1960s, the Air Force's Air Weather Service (AWS) monitored the Sun routinely for solar flares - brief intense eruptions of radiation from the Sun's atmosphere.
Solar flares often lead to electromagnetic disturbances on Earth, known as geomagnetic storms, that can disrupt radio communications and power line transmissions.
The AWS employed a network of observers at various locations in the US and abroad who provided regular input to solar forecasters at the North American Aerospace Defence Command (NORAD), a US and Canadian organisation that defends and controls airspace above North America.
On May 18, 1967, an unusually large group of sunspots with intense magnetic fields appeared in one region of the Sun. By May 23, observers and forecasters saw the Sun was active and likely to produce a major flare.
As the solar flare event unfolded on May 23, radars at all three Ballistic Missile Early Warning System (BMEWS) sites in the far Northern Hemisphere were disrupted.
These radars, designed to detect incoming Soviet missiles, appeared to be jammed. Any attack on these stations was considered an act of war.
NORAD learned the three BMEWS sites were in sunlight and could receive radio emissions coming from the Sun.
During most of the 1960s, the Air Force flew continuous alert aircraft laden with nuclear-weapons. But commanders, thinking the BMEWS radars were being jammed by the Russians and unaware of the solar storm underway, put additional forces in a "ready to launch" status, according to the study.
However, the additional aircraft was not launched, and the researchers believe information from the Solar Forecasting Centre made it to commanders in time to stop the military action, including a potential deployment of nuclear weapons.
The research appears in the journal Space Weather.
