Early warning


Une puissante éruption solaire accompagnée d’une éjection de masse coronale ont interféré avec les radars du Ballistic Missile Early Warning System du NORAD de l’hémisphère nord. Cette interférence avait été initialement interprétée comme un brouillage intentionnel des radars par les soviétiques, un acte considéré comme un acte de guerre. Des bombardiers nucléaires de contre-attaque furent sur le point d’être lancés par les États-Unis.

A powerful solar storm nearly heated the Cold War up catastrophically a half century ago, a new study suggests. The U.S. Air Force began preparing for war on May 23, 1967, thinking that the Soviet Union had jammed a set of American surveillance radars. But military space-weather forecasters intervened in time, telling top officials that a powerful sun eruption was to blame, according to the study.

« 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, » Delores Knipp, a space physicist at the University of Colorado Boulder and the study’s lead author, said in a statement. « This was a lesson learned in how important it is to be prepared. »

The storm began brewing on May 18, 1967, when researchers noticed a big group of sunspots with strong magnetic fields clumped on one part of the solar disk.

Notes on the region of the sun where the May 1967 solar flare occurred, from May 18, 20, 21, 23, and 28. (Image credit: National Solar Observatory historical archive)

That same day, all three of the Air Force’s Ballistic Missile Early Warning System radar sites in the far Northern Hemisphere — which were located in Alaska, Greenland and the United Kingdom — appeared to be jammed.

Air Force officials initially assumed that the Soviet Union was responsible. Such radar jamming is considered an act of war, so commanders quickly began preparing nuclear-weapon-equipped aircraft for launch. (These newly scrambled aircraft would have been « additional forces, » according to the study authors; the U.S. kept nuke-bearing « alert » planes aloft pretty much continuously throughout the 1960s.)


« This is a grave situation, » Knipp said. « But here’s where the story turns: Things were going horribly wrong, and then something goes commendably right. »

Those additional forces never launched. So what happened? Solar forecasters at the North American Aerospace Defense Command (NORAD) — a joint U.S.-Canadian effort that looks out for incoming missiles and other possible threats — and elsewhere figured out that the flare, not the Soviets, had disrupted the radars. (The U.S. military had begun keeping tabs on solar activity, and its effects on Earth, in the 1950s; by 1967, NORAD was getting daily updates on the subject, study team members said.)

Knipp and her colleagues think this information made it in time to Air Force commanders and other high-ranking officials — including, perhaps, President Lyndon Johnson.

« Oftentimes, the way things work is, something catastrophic happens, and then we say, ‘We should do something so it doesn’t happen again,' » Morris Cohen, an electrical engineer and radio scientist at the Georgia Institute of Technology in Atlanta, said in the same statement. « But in this case, there was just enough preparation done just in time to avert a disastrous result, » added Cohen, who was not involved in the new study.

A solar superstorm


The flare on May 23, 1967, was accompanied by a CME, which hit Earth about 40 hours later. (CMEs travel through space at millions of miles per hour — fast, but not nearly as fast as solar-flare radiation, which, of course, moves at the speed of light.)

The CME triggered a powerful geomagnetic storm, which disrupted American radio communications for nearly a week, study team members said. This storm also ramped up the northern lights, making them visible as far south as New Mexico.

« As a magnetospheric disturbance, the 25-26 May event ranks near the top in the record books, » Knipp and her colleagues wrote in the new study, which has been accepted for publication in the journal Space Weather.


The top spot in the record books, incidentally, likely belongs to the famous Carrington Event of September 1859. That geomagnetic storm caused telegraph systems to fail all over North America and Europe, and the northern lights were visible as far south as the Caribbean.

A Carrington-like storm today would likely be devastating, given how much more dependent the world is on technological infrastructure such as power grids and satellite networks, experts have said.


Atomic Samba | Photo, Thule, Greenland