July 23, 2014: If an asteroid big enough to knock modern civilization back to the 18th century appeared out of deep space and buzzed the Earth-Moon system, the near-miss would be instant worldwide headline news.
Two years ago, Earth experienced a close shave just as perilous, but most newspapers didn't mention it. The "impactor" was an extreme solar storm, the most powerful in as much as 150+ years.
"If it had hit, we would still be picking up the pieces," says Daniel Baker of the University of Colorado.
Baker, along with colleagues from NASA and other universities, published a seminal study of the storm in the December 2013 issue of the journal Space Weather. Their paper, entitled "A major solar eruptive event in July 2012," describes how a powerful coronal mass ejection (CME) tore through Earth orbit on July 23, 2012. Fortunately Earth wasn't there. Instead, the storm cloud hit the STEREO-A spacecraft.
"I have come away from our recent studies more convinced than ever that Earth and its inhabitants were incredibly fortunate that the 2012 eruption happened when it did," says Baker. "If the eruption had occurred only one week earlier, Earth would have been in the line of fire.
Extreme solar storms pose a threat to all forms of high-technology. They begin with an explosion--a "solar flare"—in the magnetic canopy of a sunspot. X-rays and extreme UV radiation reach Earth at light speed, ionizing the upper layers of our atmosphere; side-effects of this "solar EMP" include radio blackouts and GPS navigation errors. Minutes to hours later, the energetic particles arrive. Moving only slightly slower than light itself, electrons and protons accelerated by the blast can electrify satellites and damage their electronics. Then come the CMEs, billion-ton clouds of magnetized plasma that take a day or more to cross the Sun-Earth divide. Analysts believe that a direct hit by an extreme CME such as the one that missed Earth in July 2012 could cause widespread power blackouts, disabling everything that plugs into a wall socket. Most people wouldn't even be able to flush their toilet because urban water supplies largely rely on electric pumps.
Before July 2012, when researchers talked about extreme solar storms their touchstone was the iconic Carrington Event of Sept. 1859, named after English astronomer Richard Carrington who actually saw the instigating flare with his own eyes. In the days that followed his observation, a series of powerful CMEs hit Earth head-on with a potency not felt before or since. Intense geomagnetic storms ignited Northern Lights as far south as Cuba and caused global telegraph lines to spark, setting fire to some telegraph offices and thus disabling the 'Victorian Internet."
"In my view the July 2012 storm was in all respects at least as strong as the 1859 Carrington event," says Baker. "The only difference is, it missed."
