Scientists are shedding new light on a massive solar storm that narrowly missed impacting Earth two years ago. 
 
 "If it had hit, we would still be picking up the pieces," Daniel Baker of the University of Colorado said in a statement released by NASA this week. 
 
 The solar storm, which happened on July 23, 2012, was the strongest one ever recorded -- more than twice as powerful as any solar storm recorded in the last 15o years. Scientists say it was actually two storms that combined their energy into one superstorm and followed the track of another storm days earlier. 
 
 It was a close call for Earth -- the solar storm tore through Earth orbit only a week after our planet had passed by that segment of space. If we had been in its path, NASA says it would have had a "catastrophic effect," blowing out electrical systems, GPS, radio systems and other technology worldwide, plunging billions of people into a blackout that could take years to repair. 
 
 A study by the National Academy of Sciences estimates that the total economic impact of such a disaster could exceed $2 trillion. 
 
 Baker told NASA, "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 ... If the eruption had occurred only one week earlier, Earth would have been in the line of fire." 
 
 Solar storms do not pose a physical threat to people or animals or plants, just to our way of life. The real danger is a disruption of our electrical grid, satellite systems and use of modern electronics devices. 
 
 Baker and his colleagues published a study of the event in the December 2013 issue of the journal Space Weather. The storm cloud was recorded by NASA's sun-orbiting STEREO-A spacecraft. 
 
 In the February 2014 edition of Space Weather, physicist Pete Riley of Predictive Science Inc. warned that the odds of a serious geomagnetic storm hitting Earth in the next ten years was 12 percent. Riley told NASA, "Initially, I was quite surprised that the odds were so high, but the statistics appear to be correct. It is a sobering figure." 
 
 Space weather 
 
 Scientists have been tracking space weather, including solar breezes and storms, for at least 150 years. 
 
 Sunspots and solar flares lead a few hours later to a bright display of the Northern Lights. A solar wind bathes Earth all the time with a gentle, steady stream of particles. But solar storms, like analogous Earth storms, are more violent. The sun is on an 11 year solar storm cycle, with a peak for this cycle reached in 2013. 
 
 Storms have two components: large areas of violent activity called coronal mass ejections (CMEs) that are somewhat analogous to hurricanes; and powerful, focused high-speed solar flares you might think of as the solar equivalent of a tornado. Both send large numbers of high energy particles shooting away from the sun. 
 
 The Earth is surrounded by its own large magnetic field, the same field that makes a compass needle point north. Earth 's magnetic field deflects solar particles to a certain extent, but the strength of the Earth's magnetic field is decreasing, affording us less protection decade by decade. 
 
 Scientists calculate the force of a solar storm on the Earth in units called nanoTeslas (nT), with small, harmless storms hitting values near -50 nT. Prior to the July 2012 event, the most powerful known solar storm, in 1859, was estimated at -800 nT to -1750 nT, although modern measurement techniques were not available then. It knocked out telegraph machines across America. 
 
 The worst geomagnetic storm since then knocked out power across Quebec in March 1989 and registered at -600 nT. The July 2012 event would have delivered a whopping -1200 nT. 
 
 Geomagnetic storms of that magnitude could cause widespread electrical blackouts. Transformers would be destroyed if they absorbed large, sustained blasts of solar radiation that pushed them to temperatures for which they were not designed. Older transformers and those in urban areas worry experts the most since they are most sensitive to electromagnetic overloads and are hardest to replace. 
 
 Any satellite in the path of a strong solar flare could be damaged. A less serious storm harmed a pair of Canadian communications satellites in 1994; it took 6 months to repair the damage. 
 
 How do we prepare? 
 
 The U.S. National Academy of Sciences convened a workshop in 2008 to address the question: "Are our institutions prepared to cope with the effects of a 'space weather Katrina,' a rare, but according to the historical record, not inconceivable eventuality?" 
 
 By that point, many industries were already thinking about the impact of adverse space weather on their assets and operations. Since then, more technologies and procedures have been implemented. For example, the FAA can route flights away from the poles during a solar storm, and electrical grid managers can ratchet down power flow through vulnerable equipment. 
 
 The NASA spacecraft STEREO-A was able to withstand a full blast of solar radiation near the sun without harm. But not all satellites currently in use would survive. And STEREO will need to take a planned breather from its daily detailed forecasts as it moves into an unfavorable alignment with the sun this year. NASA notes there are other instruments to track solar activity, and flares should be at their low point in the solar cycle. Nonetheless, this year space weather will not be tracked in as much detail as it had been since 2006 when the pair of sun observing satellites STEREO-A and STEREO-B were launched. 
 
 But at least for the next few days, we don't have to worry. The space weather prediction is quiet, with a slight chance of a few small flares. ||||| While you didn’t see it, feel it, or even read about it in the newspapers, Earth was almost knocked back to the Stone Age on July 23, 2012. It wasn’t some crazed dictator with his finger on the thermonuclear button or a giant asteroid that came close to wiping out civilization as we know it, though — no, what nearly ended us was a massive solar storm. Almost two years ago to the day, our most bounteous and fantastical celestial body — the Sun — kicked out one of the largest solar flares and coronal mass ejections ever recorded. And it missed Earth by a whisker. “If it had hit, we would still be picking up the pieces,” says Daniel Baker, who led the research into the massive solar storm. 
 
 A solar storm is a generic term for increased activity in the Sun. In this case, the solar storm of July 2012 consisted of a massive solar flare, followed by a colossal coronal mass ejection (CME). A solar flare is initiated by the sudden release of energy stored in the Sun’s corona, causing the Sun’s plasma to heat up to tens of millions of degrees, accelerating and kicking out all sorts of radiation, and often creating a solar prominence or filament (eruption). In a large solar storm, the same energy from the corona can also cause a coronal mass ejection — a much slower-moving billion-ton cloud of plasma (electrons and protons). 
 
 Suffice it to say, but it’s bad news if the energy and plasma from a big solar flare or CME hits the Earth. Much like a man-made electromagnetic pulse (EMP) weapon, the solar energetic particles strike the Earth with such force that it ionizes the atmosphere, creating a vast cloud of energetic electrons that bounce around inside the atmosphere destroying electronics and fusing conductive wires everywhere. It would probably take out a few satellites in Earth orbit, too. 
 
 Prior to the July 2012 storm, the largest recorded storm was the Carrington Event of 1859. A massive solar flare and CME struck Earth, destroying much of the Victorian telegraph network in Europe and North America. Other solar storms have hit Earth since then, but fortunately we’ve only been hit by one large storm during modern times, which caused the 1989 Quebec blackout. The July 2012 storm was roughly twice as large as the event that caused the Quebec blackout — but fortunately, thanks to the sheer expanse of space and the Earth’s relatively large orbital distance, we dodged the bullet. “In my view the July 2012 storm was in all respects at least as strong as the 1859 Carrington event,” says Daniel Baker of the University of Colorado. “The only difference is, it missed.” [Read: Finally confirmed: An asteroid wiped out the dinosaurs.] 
 
 Rather luckily for science, though, the July 2012 solar flare and CME did hit NASA’s STEREO A satellite square on the nose. STEREO A and B are solar observation satellites that have been orbiting the Sun since 2006, providing us with all sorts of delicious imagery and science. The video above uses footage captured by the two STEREO satellites. The image at the top of the story, of a solar flare with the Earth photoshopped in for scale, was captured by NASA’s newer Solar Dynamics Observatory. Using data from these satellites, and from historical solar storms, 
 
 If the solar storm had hit Earth back in 2012, the total economic impact is estimated to be around $2 trillion, or 20 times the cost of Hurricane Katrina. It’s not just about money, though: As I covered in our feature story The Machine Stops, it would take time to fix up the world’s power grid. You can’t just magically replace dozens of giant transformers and substations. There are only so many diesel generators to fill the gap. If a giant solar storm hit the Earth, large parts of society could be without power for months or years. 
 
 Pete Riley, a physicist who looked at extreme space weather events for the last 50 years, says there’s a 12% chance that a Carrington-level storm will hit Earth in the next 10 years. 
 
 It isn’t all bad though: When we inevitably get hit by a large solar event, the resultant geomagnetic storm that wipes out most of Earth’s electronic systems will also generate some beautiful Aurorae. The Carrington Event was so powerful that the Northern Lights (aurora borealis) were seen as far south as Cuba, and the Southern Lights (aurora australis) were seen in Queensland, Australia. 
 
 At least the anarchic post-apocalyptic Earth will have a nice backdrop, then… ||||| 
 
 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. 
 
 A ScienceCast video recounts the near-miss of a solar superstorm in July 2012. Play it 
 
 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." 
 
 A report by the National Academy of Sciences details the consequences of extreme solar storms. More 
 
 A similar storm today could have a catastrophic effect. According to a study by the National Academy of Sciences, the total economic impact could exceed $2 trillion or 20 times greater than the costs of a Hurricane Katrina. Multi-ton transformers damaged by such a storm might take years to repair. 
 
 
 
 "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." 
 
 
 
 In February 2014, physicist Pete Riley of Predictive Science Inc. published a paper in Space Weather entitled "On the probability of occurrence of extreme space weather events." In it, he analyzed records of solar storms going back 50+ years. By extrapolating the frequency of ordinary storms to the extreme, he calculated the odds that a Carrington-class storm would hit Earth in the next ten years. 
 
 
 
 The answer: 12%. 
 
 
 
 "Initially, I was quite surprised that the odds were so high, but the statistics appear to be correct," says Riley. "It is a sobering figure." 
 
 
 
 In his study, Riley looked carefully at a parameter called Dst, short for "disturbance – storm time." This is a number calculated from magnetometer readings around the equator. Essentially, it measures how hard Earth's magnetic field shakes when a CME hits. The more negative Dst becomes, the worse the storm. Ordinary geomagnetic storms, which produce Northern Lights around the Arctic Circle, but otherwise do no harm, register Dst=-50 nT (nanoTesla). The worst geomagnetic storm of the Space Age, which knocked out power across Quebec in March 1989, registered Dst=-600 nT. Modern estimates of Dst for the Carrington Event itself range from -800 nT to a staggering -1750 nT. 
 
 In their Dec. 2013 paper, Baker et al. estimated Dst for the July 2012 storm. "If that CME had hit Earth, the resulting geomagnetic storm would have registered a Dst of -1200, comparable to the Carrington Event and twice as bad as the March 1989 Quebec blackout." 
 
 
 
 The reason researchers know so much about the July 2012 storm is because, out of all the spacecraft in the solar system it could have hit, it did hit a solar observatory. STEREO-A is almost ideally equipped to measure the parameters of such an event. 
 
 
 
 "The rich data set obtained by STEREO far exceeded the relatively meagre observations that Carrington was able to make in the 19th century," notes Riley. "Thanks to STEREO-A we know a lot of about the magnetic structure of the CME, the kind of shock waves and energetic particles it produced, and perhaps most importantly of all, the number of CMEs that preceded it." 
 
 
 
 It turns out that the active region responsible for producing the July 2012 storm didn't launch just one CME into space, but many. Some of those CMEs "plowed the road" for the superstorm. 
 
 
 
 A paperin the March 2014 edition of Nature Communications by UC Berkeley space physicist Janet G. Luhmann and former postdoc Ying D. Liu describes the process: The July 23rd CME was actually two CMEs separated by only 10 to 15 minutes. This double-CME traveled through a region of space that had been cleared out by yet another CME four days earlier. As a result, the storm clouds were not decelerated as much as usual by their transit through the interplanetary medium. 
 
 "It's likely that the Carrington event was also associated with multiple eruptions, and this may turn out to be a key requirement for extreme events," notes Riley. "In fact, it seems that extreme events may require an ideal combination of a number of key features to produce the 'perfect solar storm.'" 
 
 
 
 "Pre-conditioning by multiple CMEs appears to be very important," agrees Baker. 
 
 
 
 A common question about this event is, how did the STEREO-A probe survive? After all, Carrington-class storms are supposed to be mortally dangerous to spacecraft and satellites. Yet STEREO-A not only rode out the storm, but also continued taking high-quality data throughout. 
 
 "Spacecraft such as the STEREO twins and the Solar and Heliospheric Observatory (a joint ESA/NASA mission) were designed to operate in the environment outside the Earth's magnetosphere, and that includes even quite intense, CME-related shocks," says Joe Gurman, the STEREO project scientist at the Goddard Space Flight Center. "To my knowledge, nothing serious happened to the spacecraft." 
 
 The story might have been different, he says, if STEREO-A were orbiting Earth instead of traveling through interplanetary space. 
 
 "Inside Earth's magnetosphere, strong electric currents can be generated by a CME strike," he explains. "Out in interplanetary space, however, the ambient magnetic field is much weaker and so those dangerous currents are missing." In short, STEREO-A was in a good place to ride out the storm. 
 
 
 
 "Without the kind of coverage afforded by the STEREO mission, we as a society might have been blissfully ignorant of this remarkable solar storm," notes Baker. "How many others of this scale have just happened to miss Earth and our space detection systems? This is a pressing question that needs answers." 
 
 If Riley's work holds true, there is a 12% chance we will learn a lot more about extreme solar storms in the next 10 years—when one actually strikes Earth. 
 
 Says Baker, "we need to be prepared." 
 
 Credits: 
 
 Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit: Science@NASA
– Imagine life without electricity or running water, and you'll understand what nearly befell our planet two years ago. Scientists say that on July 23, 2012, the sun belched its biggest solar flare in more than 150 years and barely missed us, CBS News reports. A week earlier and the storm would have struck Earth on its orbit with "catastrophic" effects, NASA says, blacking out radios, damaging satellite communications and GPS, and "disabling everything that plugs into a wall socket." Such a flare wouldn't hurt human life directly, and the Southern and Northern Lights would be gorgeous, but the blast's mix of X-rays, extreme UV radiation, energetic particles, and massive clouds of magnetized plasma would cause an estimated $2 trillion in damage. It would also leave "large parts of society" crippled for months or years while workers replaced major transformers and substations, ExtremeTech reports. The sun, on an 11-year solar-storm cycle, has nearly done this before: A massive storm called the "Carrington Event" struck Earth in 1859 but couldn't inflict much electrical damage in the age of steam engines (telegraph lines did spark and set fire), and a pretty powerful storm caused blackouts across Quebec in 1989. One physicist says there's a 12% chance of a big solar blast hitting us over the next decade, which he calls a "sobering figure." Another is quoted in the Guardian saying how lucky we are that the blast wasn't in sync with our orbit: "Earth and its inhabitants were incredibly fortunate that the 2012 eruption happened when it did," he says. "We'd still be picking up the pieces." (Read about the sun's newly discovered "long-lost brother.")