Near Miss: The Solar Superstorm of July 2012   
       
   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.   
       
   https://www.youtube.com/watch?v=7ukQhycKOFw   
       
   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."   
       
   http://tinyurl.com/28w978g   
       
   A report by the National Academy of Sciences details the consequences of   
   extreme solar storms. MoreA 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 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   
       
   Web Links:  Severe Space Weather: Social and Economic Consequences --   
   Science@NASA   
       
   Carrington-class Solar Storm Narrowly Misses Earth -- ScienceCast video   
      
   --- D'Bridge 3.99   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)