Cold War tensions were high on May 23, 1967, when a colossal solar storm reportedly brought the United States and Soviet Union to the verge of nuclear war. The extreme solar flare, or burst of radiation in short wavelength, severely impaired communications near military bases in parts of the Arctic and North America, including at North American Air (now Aerospace) Defense Command (NORAD) in Colorado.
At roughly the same time, an extraordinary solar radio burst disrupted NORAD’s Ballistic Missile Early Warning System (BMEWS), the primary radar system used by Canada and the U.S. to scan Arctic skies for intercontinental ballistic missiles and potentially hostile aircraft. Thirty-six hours after the burst, a coronal mass ejection (CME) — an eruption of magnetized plasma from the sun’s outer atmosphere — arrived at Earth with such force that, had it occurred today, it would have registered as a G5 storm — among the most intense on the National Oceanic and Atmospheric Administration’s (NOAA) geomagnetic storm scale.
With the sun now in the middle of Solar Cycle 25 — a period of intense solar activity expected to last through 2030 — discussions have arisen about whether another 1967-style incident is around the corner and, if so, whether it would similarly affect electrical systems. At the time, the effects of solar weather were just beginning to be understood. While much of North America marveled at the resulting aurora — The Washington Post published an article, “City Gets Rare Look at Northern Lights” — U.S. commanders were privately expressing alarm about disruptions to communications and radar equipment.
The radar interference — triggered by the radio burst — was so severe that military leaders initially mistook it for electronic jamming by a foreign adversary, a potential act of war. In response, the Air Force’s Strategic Air Command (SAC) — which through the 1960s maintained a fleet of nuclear-equipped long-range bombers — reportedly ordered air crews to warm up their engines and taxi toward the runway. But cooler heads prevailed. The Air Force’s relatively new Air Weather Service (AWS) — which only a year earlier published its first manual on forecasting solar storms — observed the solar burst and managed to convince military leaders that the radar disruption was likely due to extreme space weather. Bomber crews were ordered to power down their engines, and what might have become a catastrophe was averted.
“It is well worth noting that during the politically tense days of late May 1967 a full out aircraft launch by western forces could have been very provocative and, just as importantly, difficult (if not impossible) to recall in the greatly challenged HF-UHF radio environment,” wrote the authors of a 2016 article about the incident published in Space Weather, a journal of the American Geophysical Union.
The article, “The May 1967 great storm and radio disruption event: Extreme space weather and extraordinary responses,” analyzed data and scientific reports of the era while also bringing together individuals who recounted their experiences. “From the totality of the reports … we can understand that radio communications and radar monitoring during the early to middle afternoon hours (local time) of 23 May in the central U.S. and Canada were subject to significant interference and signal loss,” they wrote. “Simultaneously, some of the fixed, high-latitude BMEWS radar faces directly pointed at the setting Sun as it produced record level radio emissions. Even BMEWS faces with non-Sun-directed orientations likely had side and back lobes that were subject to solar RFI [radio frequency interference].”
For decades, the storm’s potential impact on society remained largely unknown. Scientific studies about the geomagnetic effects of solar weather were limited at the time, and given the political climate and technology of the day, it wouldn’t have seemed unreasonable to interpret a solar-based disruption as an attack on long-range sensors. Worries about Soviet jamming were real and persistent, and the Cuban missile crisis, only five years earlier, still resonated in people’s minds. Against this backdrop, nuclear armament — another byproduct of Cold War tensions — stood at an all-time high, with the U.S. deploying roughly 31,255 nuclear weapons around the world. That compares with 5,044 U.S. nuclear warheads today, according to the Federation of American Scientists.
However, at the time, just enough was known by the Air Force’s forecasters to make a convincing case about the effects of coronal bursts on radar and communications equipment. Credit for the correct diagnosis, the report’s authors said, should go to Air Force Col. C.K. Anderson and “his NORAD solar forecasting staff (in particular Major Donald Sherry and Captain Lee Snyder),” who provided information at a critical point in history that “calmed nerves and allowed aircraft engines to cool as they returned to normal alert stance.”
“With the limited data available at the time, AWS solar forecasters were able to extract sufficient information from AFCRL [Air Force Cambridge Research Laboratories] solar observations to convince high-level decision makers at NORAD that the Sun was a likely culprit in contaminating the BMEWs radar signals,” the article said.
In a joint news release ahead of the article’s publication, the American Geophysical Union and the University of Colorado Boulder wrote that the 1967 solar storm remains a classic example of how geoscience and space research are essential to U.S. national security.
“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,” lead author Delores Knipp said in the release. “This was a lesson learned in how important it is to be prepared.”
Morris Cohen, an electrical engineer and radio scientist at Georgia Institute of Technology in Atlanta, observed that the public is likely unaware of the potential for natural disasters to mislead military forces into thinking they’re under attack. Fortunately, he said, the May 1967 storms brought about change as a near miss rather than a full-blown catastrophe. “Oftentimes, the way things work is [that] something catastrophic happens and then we say, ‘We should do something, so it doesn’t happen again,’” Cohen, who was not involved in the study, said in the release. “But in this case, there was just enough preparation done just in time to avert a disastrous result.”
In the aftermath, U.S. military leaders took steps to avoid another such episode. Support for SAC and other command authorities accelerated and broadened, leading to the formation of a Space Environment Support System (SESS) category of “weather officers” to receive additional/special education about the space environment.
Within months of the May 1967 storms, a formal AWS ionospheric section was stood up to support ionospheric-dependent systems, including the first supported operational system: the “440 L over-the-horizon radar,” which operated over the Eurasian continent. In late 1968, the AWS unveiled an SESS organizational plan that consolidated several space-monitoring systems, including the Solar Observing and Forecasting Network (SOFNET), which at the time was tasked with supporting NORAD and its radars, the article said.
By 1969, ionospheric forecasting had been expanded to a 24-hour operation. The effort became so computer-intensive that in 1973 the military opted to move the SESS Forecast Center to Air Force Global Weather Central at Offutt Air Force Base, Nebraska, to take advantage of the increased computer power there, Knipp said. This had the added benefit of being in closer alignment to SAC, also based there. In addition, in 1972 the AWS and NOAA agreed to combine their space forecasting efforts, creating a partnership that extends to this day.
“Since 1967, we’ve learned that solar flares are only one way that the sun erupts,” Knipp told Apogee. “Sometimes, accompanying solar flares are streams of highly energized particles, mostly relativistic protons, that can blind sensors and/or bury themselves deep in satellite components and cause damage from the inside.
“These same energetic particles cause Earth’s ionized upper atmosphere in the polar regions to absorb radio signals that would otherwise travel through the region,” she said. “This happened in 1967 and continues to disrupt HF [high frequency] polar communications on occasion, even recently. Forecasters can only give short-term predictions of such events because the particles are traveling at near light speed.”
Still, despite technological advances and our enhanced understanding of space, could the military again be fooled into thinking an attack is imminent? Scientists say it’s doubtful a 1967-style incident could occur again. “I’d say that it is much less likely now that a space weather event could trigger a military attack,” Senior Astrophysicist Kathy Reeves from the Center for Astrophysics, Harvard & Smithsonian, told Apogee.
“In the ’60s, space weather monitoring was in its infancy, but today it is much more sophisticated, and there is more information readily available about the geomagnetic environment and its response to solar storms,” she said. “These days, NOAA has an entire department dedicated to space weather prediction.”
Knipp agreed, noting the array of technologies available to scientists today to help them more effectively monitor solar activity. “I believe the likelihood of mistaking a solar ‘flare’ signal for an ‘act of war’ signal is reduced compared with the situation in 1967,” Knipp said. There are more eyes on the sun from sensors in varied wavelengths on different ground and space platforms. “Many nations host their own or U.S. solar assets, so solar signals are monitored in some way 24/7.”
However, that doesn’t mean technology is completely immune to the effects of geomagnetic storms and solar radiation, or that occasional communication lapses don’t still occur, even today.
“I won’t say ‘never,’” Knipp said. “In 1972, we had Navy solar X-ray sensors in space, but the sun produced such a huge flare on August 4 that the sensor was saturated. Radio communication across many wavelengths was impossible.
“As a science community, we really don’t understand these events very well, nor do we recognize their precursors. In December 2006, the sun pulled such a stunt – this time with a radio burst [a radio wavelength flare] that saturated ground-based GPS sensors on Earth’s dayside. To counter that, more frequencies were added to GPS and other Global Navigation Satellite Systems.”
Similarly, she said, in December 2023, a flare broadly affected aviation across North America, impacting VHF/UHF communications for commercial planes and air traffic control. “A lot of frequency adjustments were made to keep information flowing.”
One of her chief concerns is about the multidimensional impact that CMEs pose for satellites in low Earth orbit, UHF and VHF communications on the ground and on the nation’s power grid.
“These [CMEs] are lumbering giants that, if Earth-directed, arrive at Earth in one to four days and impact Earth’s magnetic field,” she told Apogee. “In May 2024, we saw the effects of a series of these piled up … The most geo-effective of these produce auroral, power grid disturbances and upheaval in Earth’s heated upper atmosphere, the latter of which result in substantial satellite drag. This concern was generally documented in the Space Weather Advisory Group User Needs Survey published in September of 2024. Problems with satellite drag occurred in May of 2024, as it has with most other large geomagnetic storms. Some of the problems in civil spacecraft fleets are now coming to light.”
She added: “It’s not hard to imagine an adversary taking advantage of any of those situations during tense times.”