Ian Evenden explains how the Sun could one day take out our electronics and communications technology in mere moments

© GETTY IMAGES/ MARK GARLICK/SCIENCE PHOTO LIBRARY

EARTH, SEPTEMBER 1ST, 1859. Colors flash through the night sky above New England, gold miners in the Rocky Mountains are woken by the brightness of the Northern Lights, visible as far south as the Caribbean. Telegraph operators across the world receive electric shocks from their equipment, which continues to operate, despite being disconnected from the power supply.

The Sun, August 31st, 1859. A complex system of magnetic field lines suddenly twists, releasing a large quantity of plasma into space. This takes 17 hours to cross the 93 million miles to the Earth, which is at just the right place in its orbit to be hit by what today we’d call a coronal mass ejection.

The largest geomagnetic storm on record, the Carrington Event caused widespread electrical disruption and power blackouts in an electrical grid that was primitive compared to today’s complex system.

Should it happen again, the consequences could be catastrophic. A 2013 research project from Lloyds of London and Atmospheric and Environmental Research in the United States estimated the cost to the US alone could be $2.6 trillion.

At the peak of its activity, the Sun belches out as many as three coronal mass ejections every day. One only just missed us in 2012, and if it struck today, the damage would be incalculable.

WHAT’S IT ALL ABOUT?

In their day-to-day lives, our PCs and other electrical equipment are unlikely to come into contact with charged particles, but every now and then, the Sun reaches out to touch us. Protected in the Earth’s magnetic bubble, we don’t often notice the effects of the solar wind unless we live far enough north (or south, hello readers in New Zealand) to see the aurora. Our Sun is, compared to other places in the Universe, a relatively placid, middle-aged star, but occasionally it can surprise us.

The Sun operates on an 11-year cycle. In 1859, it was approaching the middle of this cycle, the time of greatest activity. Astronomers, equipped with everimproving telescopes, were starting to take more of an interest in the Sun around this time, and the first observation of a solar flare was made on September 1st that year by the astronomers Richard Carrington (for whom the solar storm is named) and (independently) Richard Hodgson, both based in southern England.

That flare, which Carrington observed by projecting the output of his telescope onto a screen through a broad-band filter (remember, never look at the Sun with the naked eye, or with any kind of magnifying equipment, or indeed with anything other than an approved solar filter) turned out to be enormous, a white light flare of extraordinary intensity.

Solar flares are associated with coronal mass ejections, and both are common when sunspots are on display, as these temporary, dark patches are signifiers of magnetic activity on the star’s surface. As the 11-year cycle goes on, the sunspot count moves from none, sometimes for hundreds of days at a time, to anything up to several hundred at once.

OF SUNSPOTS AND CMES

Nobody was counting sunspots in 1859, though they were known to Chinese astronomers back in antiquity, and were mentioned by the Ancient Greeks. They were first drawn (that we know of) by an English monk in 1128. It took until 1610 to get a telescope on them, which is fair enough as the instrument was only patented in 1608, but it wasn’t until the early 1800s that the astronomer William Herschel was able to associate sunspots with varying levels of solar activity. His hypothesis that an absence of sunspots led to higher wheat prices on the market, was widely ridiculed at the time.