Engineering for an Unseen Invasion
If the headline had appeared in the National Enquirer or some such tabloid, no one would have thought it remarkable. But it turned up in the newspaper published by the Institute of Electrical and Electronics Engineers, and in a professional publication it did catch the eye: "Utilities engineers meet to discuss invisible threat from outer space."
What alarmed the engineers was not an invasion of bug-eyed monsters or little green men, but it did arrive unseen from a source beyond Earth, and it did cause big trouble. The same gigantic flare on the sun that brought Alaska a red aurora this past March brought problems to utilities engineers from California to Sweden. Transformers overheated, relays tripped spontaneously, capacitor banks misbehaved.
Those were the minor nuisances. In Canada, the solar flare led to a power outage for virtually the whole province of Quebec.
The villain in these problems is known as geomagnetically induced current, GIC for short. It does indeed start with events on the sun, but the earth has more than a passive role in producing these currents.
Anyone who has used a compass is familiar with the idea that Earth is a big spherical magnet. So is the sun. Most northerners, at least those interested in the aurora, also understand that the sun is constantly emitting a high-speed rain of particles into space--the solar wind. When the sun is especially active, its corona discharges even more particles, traveling even faster; the solar wind becomes gusty.
Most aurora-watchers can leave it at that--a look skyward, a wise nod, and a comment: "Yup, good northern lights tonight. Must be a gusty solar wind blowing in from the right direction." Auroral scientists and electrical engineers carry it a bit farther. The solar wind carries more than streams of particles. It's also an extension of the sun's magnetic field.
What happens in this real-life game of Space Invaders is that Earth's magnetic field serves as a shield against the incoming solar particles and magnetic field. It's not a perfect shield, since some of the solar field lines link with Earth's magnetic field, but most of the particles and field sweep around our planet. We end up encased in an invisible shell (really, it is a kind of force field) shaped like a comet, round head, tapering long tail: Earth's magnetosphere.
There are plenty of clues that the magnetospheric interactions vary. Auroral activity is one highly visible sign, but short-wave radio upsets and compass misbehavior also point out the changeable nature of the natural magnetic fields surrounding us. Given enough activity on a portion of the sun appropriately positioned to affect Earth, the engineers and scientists begin talking of geomagnetic storms.
Check an unabridged dictionary, and you'll find something like: "induced current: a current produced in a conductor by a variation in the intensity of the magnetic field through which it passes." What better conductor than a power line? And a power line extending for hundreds of miles, bathed in unseen but changing magnetic fields because of all that energetic activity far overhead, could certainly find itself carrying quite a charge of induced current--certainly enough to trip protective devices.
That, in a nutshell, is the story of a real invasion from space. As the electrical engineers sadly concluded, there's little they can do except brace themselves for more bursts of geomagnetically induced currents. The sun has another year or two of increasing activity to go on this cycle, and they expect problems will increase right along with it. In fact, another set of intense solar flares occurred on August 10-11 and 13-14 this year. Short wave propagation on transpolar paths was severely disrupted for about 10 days. Some auroras were sighted over Fairbanks near midnight, even though the sky wasn't completely dark.
Northerners can enjoy the auroras we're bound to get--but should keep plenty of flashlight batteries on hand.
