Lull before the storm?

Last Updated 25 March 2013, 14:00 IST

If a sun storm similar to the one that erupted in 1859 strikes again, some telecomunications satellites would be disabled   and GPS signals scrambled. The surge of electricity from the ground would threaten electrical grids, plunging a couple of continents into darkness. Scientists say it is impossible to predict when the next solar storm would erupt in a sunspot cycle that will soon reach its crest, writes Kenneth Chang.

In 1859 the sun erupted, and on earth wires shot off sparks that shocked telegraph operators and set their paper on fire. It was the biggest geomagnetic storm in recorded history. The sun hurled billions of tons of electrons and protons whizzing towards the earth, and when those particles slammed into the planet’s magnetic field they created spectacular auroras in the night skies — along with powerful currents of electricity that flowed out of the ground into the wires, overloading the circuits.

If such a storm struck in the 21st century, some telecommunications satellites high above the earth would be disabled; GPS signals would be scrambled. The surge of electricity from the ground would threaten electrical grids, plunging a continent or two into darkness. Scientists say it is impossible to predict when the next monster solar storm will erupt and whether the earth will lie in its path. What they do know is that with more sunspots come more storms, and this fall the sun is set to reach the crest of its 11-year sunspot cycle.

Sunspots are regions of turbulent magnetic fields where solar flares originate. Experts are divided on the consequences of a cataclysmic solar eruption, known as a Carrington event, for the British amateur astronomer who documented the 1859 storm. A continent-wide blackout would affect many millions of people, “but it’s manageable,” said John Moura of a nonprofit group founded by utilities to help manage the power grid.

Still, this sunspot cycle has been quieter than most. Even if the sun unleashes a huge
burst, as it did last July, the odds are that it will head harmlessly in some other direction into the solar system. “There’s always the chance of a big storm, and the potential consequences of a big storm has everyone on the edge of their seats,” said William Murtagh, programme coordinator for the Space Weather Prediction Center, part of the National Oceanic and Atmospheric Administration.

A huge power trip

The most studied, unambiguous example of the sun’s ability to snarl power grids occurred on March 13, 1989 in Quebec. In the early-morning hours, a solar storm generated currents in the transmission wires, tripping circuit breakers. Within minutes, a blackout stretched across the province, shutting down businesses, schools, airports and subways until power was restored later that day. Canada was hit again a few months later, when another solar storm was blamed for computers shutting down at the Toronto Stock Exchange, halting trading.

“There’s a sense in the field that we don’t have all the answers,” said Antti Pulkkinen, a scientist at the NASA Goddard Space Flight Center in Greenbelt, Md.

Solar flares, travelling at the speed of light, arrive on earth in less than 8.5 minutes and can drown out some radio communications. But it is the coronal mass ejections — in which billions of tons of electrons and protons are disgorged from the sun and accelerate to over one million miles per hour — that cause more worry.

The particles, which take two or three days to travel the 93 million miles from the sun to the earth, never hit the surface; the planet’s magnetic field pushes them aside. But then they are trapped in the field. The back-and-forth sloshing generates new magnetic fields, mostly over the night side, and they, in turn, induce electrical currents in the ground. Those currents surge out of the ground and into the electrical transmission lines. “In a sense, we’re playing Russian roulette with the sun,” said John Kappenman, an electrical engineer who has been warning of potential catastrophe.

Not an easy cycle to comprehend

This solar cycle has so far defied easy understanding. It started late — so late that some speculated that it was the beginning of an extended quiet period, like in the mid-1600s, when almost no spots blemished the sun for decades. It has been quieter than many experts expected, and so far it appears to have peaked early. The two hemispheres of the sun are out of sync.

The northern hemisphere has been ahead of the curve, producing a large number of sunspots in late 2011 and has quieted since then, while the southern hemisphere has remained fairly quiet throughout. Most solar scientists expect the southern hemisphere to perk up, and the number of sunspots to increase again, with the solar maximum arriving in the fall.

Such double-peak patterns have appeared in some earlier solar cycles, including the last one.

“I believe I can say with strong confidence there will be a second peak in 2013,” said Douglas Biesecker, a physicist at the Space Weather Prediction Center and the chairman of a panel that issued predictions about the solar cycle. In the past year, about 20 have reached the earth. The sun’s huge eruption in July 2012 was aimed the wrong way, luckily for the earth, but it did cross one of NASA’s sun-watching craft, known as Stereo.

Feeling blindsided

On the morning of Sept. 1, 1859, British amateur astronomer Richard C Carrington was sketching a large group of sunspots when he saw a blinding white flash engulf them: a solar flare. The magnetic currents that generated the flare also set off a coronal mass ejection. When the particles arrived on the earth fewer than 18 hours later, they created an electrical current that overwhelmed telegraph circuits.

A telegraph operator in Washington reported that his forehead grazed a ground wire and “immediately, I received a very severe electric shock,” and “an old man who was sitting facing me, and but a few feet distant, said that he saw a spark of fire jump from my forehead to the sounder.”

NASA’s sun-watching spacecraft keep track of sunspots, and they can provide some warning of which regions look likely to erupt. While the craft can tell how large an eruption is, they cannot make one important determination: which way the magnetic field is pointing within the swarm of particles. If the field is pointing north, the earth’s magnetic field can absorb the shock fairly well. But if the field is facing south, in the opposite direction from the earth’s field, the magnetic fields snap and reconnect — magnetic “short circuits” that release huge bursts of energy.

NASA has one satellite, Advanced Composition Explorer or ACE, that can tell which way the field is pointing. But Ace is just 900,000 miles from the earth, at a spot where the gravitational pull between the sun and earth cancel. When it makes that crucial measurement, a giant, fast-moving coronal mass ejection could be just 10 minutes away.
Utility companies would have to quickly make their final decisions – and perhaps deliberately cause a continentwide blackout – in order to protect the electrical grid from greater damage.

(Published 25 March 2013, 14:00 IST)

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