"It begins on the sun's surface: a broad, hellish plain of boiling 5,700 degree gas. Powerful magnetic fields arc upwards from the surface, rising high into the solar atmosphere to form giant, twisting arcades of energy. Matter streams up these arches to be gripped in a magnetic vise a million miles above the surface. Then something happens. Something shifts. Magnetic lines of force in the arcade snap like steel cables on the bridge to heaven. Billions of tons of solar gas are suddenly blown outward, exploding across interplanetary space. Three days later the shimmering ball of energy smashes head-on into the unsuspecting Earth.
While the paragraph above might sound like the beginning of a bad science fiction movie it's really nothing more than a slightly hyperbolic description of the last three days. The only error in my description of the solar storm that struck us today is that we were not caught unawares. We have been watching the whole time. In that fact lays a deeper truth speaking to much more than solar activity.
Yesterday I received an email from NOAA's Space Weather Prediction Center. They had issued a watch for a "geomagnetic storm" associated with a bright flare on the sun Sunday evening. The expectation was that storm would arrive today "with possible impacts to navigation, the power grid and satellites." NOAA says it's the most powerful such event to hit Earth since 2005.
Space weather, as it is called, originates with solar magnetic activity. The sun is a giant spinning ball of charged particles. In addition to its spin, the heat released from the core through nuclear fusion eventually sets the upper layers of the sun into a kind of boiling motion called convection. All that motion — spin and convection — means lots of charged particles streaming this way and that. Since current (the flow of charges) produces magnetic fields, the outer domains of the sun are ruled by magnetism. Magnetic fields are the source of all those cool images of giant flares erupting in planet-spanning arcades of super-hot plasma. It's also the source of so-called Coronal Mass Ejections or CMEs, which are, essentially, the space storms that space weather is all about.
CMEs are eruptions of matter and magnetism from the sun into space. A typical CME will blow 10 billion kilograms (about 22 billion pounds) of solar plasma into space along with enough energy to represent a flotilla of 220 aircraft carriers moving at 500 km/s. The fact the CME's are quite common says a lot about the power locked up in an ordinary star like the sun.
While 1 to 3 CMEs may occur every day, we only notice the ones that slam into the Earth on their journey across the solar system. When a CME crosses the Earth it runs into our planet's own magnetic field. Charged particles from the CME get trapped by the Earth's magnetic field and stream down toward the planet's surface near the poles.
When those CME particles, running down magnetic field lines, strike atmospheric gas atoms, the collisions cause the atoms to light up like Christmas tree bulbs. That is the origin of the simmering walls of color we called aurora. There was a time when pretty lights were all there was to space weather. Those days are over.
Before we became a high-tech culture, the collision of the CME with the Earth was no cause for alarm. Now space weather poses serious risks for everyone. For astronauts, the torrent of high-energy particles pose health risks via heavy doses of ionizing radiation. Orbiting satellites used for communications, weather prediction and a 100 other purposes can feel the blow too, as CME particles destroy solar panels and sensitive electronics.
Sprawling grids of power-lines on Earth can also feel the effect of all that CME current dumped suddenly into the atmosphere. Electric grids can overload and, without warning, millions of people might be plunged into darkness (as occurred in 1989, when a severe space storm caused a system-wide power failure in Quebec).
To deal with the problem, NASA and other space agencies have begun to continually monitor the Sun. As soon as a CME is observed, powerful supercomputers are engaged to predict its path through space. If the storm of matter and magnetism appears headed toward Earth then precautions can be taken like bringing astronauts in from space walks or putting satellites into "safe-modes" where their electronics will be less likely to suffer damage.
While there is enough remarkable science related to space weather to fill 20 blog posts, I want to end this description with the briefest of thoughts which never fails to astonish me. For thousands of generations the human habitation of this planet knew nothing of space weather. We knew Earth-bound winds and even learned to use those winds to become a sea faring race. When gossamer veils of light appeared in the northern skies we watched, wondered and prayed and then went about our business.
Now we have crossed a threshold. Now we have become a high-tech, space-faring race encircling the planet's surface with power-lines and its skies with orbiting satellites. There are other winds and other storms we must now be attentive to as we go about our business. In this way, as in so many others, our long childhood as a species has ended for better or for worse."