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Gone with the [Solar] Wind

February 17, 2012

The world is experiencing spectacular displays of aurora borealis, stretching to countries which rarely experience them, like the U.K., and, in the photo to the right, the American Midwest.  These graceful and mysterious lights inspired transcendentalist poet Christopher Pearse Cranch to write:

Who can name thy wondrous essence,
Thou electric phosphorescence?
Lonely apparition fire!
Seeker of the starry choir!
Restless roamer of the sky,
Who hath won thy mystery?
Mortal science hath not ran
With thee through the Empyrean,
Where the constellations cluster
Flower-like on thy branching lustre.

Cranch might not have been so enraptured had he known the aurora borealis is caused by solar flares.  The latest IEEE Spectrum has an article on the damaging effects of solar flares, and friends, seeking starry choirs is the least mischief these electric phosphorescences intend.  But as overwrought as he was, Cranch did get the electric part right.  Solar flares occur when the Sun ejects massive amounts of material – on the order of a billion tons – in the form of charged particles, outwards with great force.  These particles – electrons and protons – do 2 things: First, the particles beat back the shielding magnetic field of the Earth and create charged plasma in the upper atmosphere, called an electrojet.  Current in the electrojet can exceed millions of amperes; these high-up currents can induce smaller, damaging currents at ground level.

Second, the impact on the magnetosphere causes waves in the Earth’s magnetic field.  These waves are powerful enough to create GICs – geomagnetically induced currents – just as spinning a magnet inside a copper coil induces a current.  GICs can be 100s of amps per incident.

Most of the time, these two effects are small, limited only to Cranch’s lonely apparition-type fires.  But sometimes, these flares are really big.  In 1989 all of Quebec was blacked-out in 30 seconds; its grid experienced 15 simultaneous failures and that instantly cascaded into province-wide failure.  Bad as that storm was, there are recorded events of storms even bigger, including an 1921 storm that blanketed all of North America and most of the Pacific, and an 1859 storm that was much larger still.  2012-2013 will see the solar max, a period of increased sunspot activity, and also of increased solar flares.

The entire world is considerably more electrified today than even in 1989, and very much more than in 1921.  That means we are all the more vulnerable.  Nuclear power plants are exceptionally vulnerable because of the very large number of transformers and lines that service a nuclear facility.  An 1989 or greater size storm that hits the US East Coast could have devastating effects.

The Spectrum sounds a hopeful note, however: Transformers can be protected from GICs with new, relatively inexpensive technology.  Will we do it, though?  I have to say, unlikely – it is more in our social nature today to risk billions or even trillions in damage, rather than spend millions in prevention.

Cranch went on to write:

Is not human fantasy,
Wild Aurora, likest thee,
Blossoming in nightly dreams,
Like thy shifting meteor-gleams?

Here’s hoping that the auroras of this year and the next bring us no more than fantastic dreams.

Categories: Science
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