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COLUMN

Time to be afraid - preparing for big solar storm

London, July 27, 2014

By John Kemp

The probability of a solar storm striking Earth in the next decade with enough force to do serious damage to electricity networks could be as high as 12 per cent, according to solar scientists.

One such storm erupted from the surface of the Sun two years ago, on July 23, 2012. If it had been directed at this planet, it would have produced the worst geomagnetic storm in more than four centuries and caused extensive power problems.

Fortunately, on this occasion, the eruption pointed away from Earth and the storm blasted safely out into space.

But if it had occurred just a week earlier, when the site was pointed directly at our planet, billions of tonnes of highly charged particles would have raced towards Earth's magnetic field at a speed of 2,500 km per second.

The result would have been a spectacular display of the northern lights (aurora borealis) and southern lights (aurora australis) visible as far as the equator, turning the night sky as bright as daytime.

But it could also have fried the world's electricity grids and left hundreds of millions of customers without power for months or even years.

In the event of an eruption directed at Earth, politicians and power grid operators would have just a few hours from the first signs until the full fury of the storm hit to protect the electrical systems on which modern life depends.

"The July 2012 solar storm was a shot across the bows for policymakers and space weather professionals," US solar researchers warned in the journal Space Weather.

"Our advanced technological society was very fortunate, indeed, that the solar storm did not occur just a week or so earlier. Had the storm occurred in mid-July the Earth would have been directly targeted ... and an unprecedentedly large space weather event would have resulted."

"There is a legitimate question of whether our society would still be picking up the pieces," they concluded.

THE NEXT BIG ONE

Scientists and power grid operators remain divided over how much damage the power grid would suffer in a severe solar storm aimed directly at Earth.

A moderately severe geomagnetic storm aimed at the United States could cut power to 130 million people and damage more than 350 high-voltage transformers, which would take months to replace, according to a report published by the US National Academy of Sciences in 2008.

A really severe storm could inflict damage and disruption estimated at between $1 trillion and $2 trillion, 20 times the cost of Hurricane Katrina, with a full recovery time between four and 10 years, the academy wrote  ("Severe space weather events: understanding societal and economic impacts", 2008).

"The loss of electricity would ripple across the social infrastructure with water distribution affected within several hours; perishable foods and medications lost in 12-24 hours; loss of heating/air conditioning, sewage disposal, phone service, fuel re-supply and so on," according to a study funded by the US government.

Older electrical transformers would be at particular risk of being damaged by the enormous electrical currents induced in the power grid by a severe storm.

Transformers cannot just be ordered from a store. Spare units are in limited supply. Ordinarily, it takes up to 15 months to order, manufacture, install and test a high-voltage transformer - even longer for some specialised equipment.

"The need to suddenly replace a large number of them has not been previously contemplated," the US government's Oak Ridge National Laboratory warned in 2010 ("Geomagnetic storms and their impacts on the U.S. power grid", January 2010).

The problem is not just manufacturing. High-voltage transformers are exceptionally large and heavy, so they have to move slowly by ship, road and rail, and cannot be air freighted. Moving one even a few kilometres requires weeks of planning.

"It may take one week to move a 250,000-volt transformer a short distance in major metropolitan areas," Oak Ridge explained. "Even the distance of a few miles may take an entire weekend, as a number of traffic lights have to be removed and reinstated as the load is moved at snail's pace in special trailers and the route taken has to be fully surveyed for load-bearing capability by civil engineers."

Grid operators are more sanguine about the risks. Severe geomagnetic storms are more likely to cause blackouts and short-term power loss, rather than permanent damage, according to a report prepared by the North American Electric Reliability Corporation (NERC) on behalf of the industry ("Effects of geomagnetic disturbances on the bulk power system", February 2012).

NERC thinks a severe storm would heat up a fully loaded transformer to around 120 degrees Celsius for roughly four minutes, well below the 200-degree design threshold used for modern equipment. A really severe storm could push temperatures over 200 degrees for 14 minutes, potentially causing failures, but is unprecedented in modern times, according to NERC.

Nonetheless, the industry has established a special working group on mitigating the effects. And in May 2013, the Federal Energy Regulatory Commission formally directed NERC to develop reliability standards to help protect the U.S. grid from solar storms ("FERC Order 779: Reliability standards for geomagnetic disturbances", May 16, 2013).

CARRINGTON EVENTS

NERC characterises severe geomagnetic storms as "high impact, low frequency" (HILF) risks. High impact, low frequency risks are particularly hard to manage because policymakers must decide how much money to spend on reducing a risk that would be catastrophic but seems remote.

However, recent research suggests the probability of a severe storm hitting Earth may be much higher than NERC assumed.

The worst solar storm on record occurred on September 1, 1859, and was observed by an amateur astronomer in England called Richard Carrington, after whom the Carrington Event is named.

A large solar flare erupted from the surface of the Sun lasting for around five minutes. At the same time, a huge mass of highly charged particles, known as a coronal mass ejection (CME), was flung towards Earth at speeds up to 2,000 km per second, according to reconstructions by modern solar scientists.

The first particles reached Earth within an hour and the storm peaked around 17 hours and 40 minutes after the flare was observed.

The Carrington Event occurred in a largely pre-electrical age, so the impact was limited. But it was strong enough to damage severely the new telegraph systems installed in North America and Europe.

The next big solar storm, reported in May 1921, brought the US telegraph service to a halt between the East Coast and the Mississippi River, blowing fuses and burning some operators.

In March 1989, a severe geomagnetic storm blacked out Quebec's power grid in less than two minutes - the worst impact to date.

In October and November 2003, the so-called Halloween storms caused isolated transformer failures in North America and Europe.

Measuring the severity of a storm is tricky because it depends on so many factors, including the size of the flare, the scale of coronal mass ejection, the speed at which it travels from the Sun to Earth, magnetic flux, time of day, and location of the direct hit.

But one common summary statistic used by solar researchers is called "disturbance-storm time", or Dst for short.

The Dst index measures how hard Earth's magnetic field shakes when a storm hits, according to NASA ("Near miss: the solar superstorm of July 2012").

Dst is measured in nano-Teslas (nT). The more negative Dst becomes, the worse the storm.

The Carrington Event in 1859 is estimated to have had a Dst index of around -850 nT. The Quebec storm in 1989 clocked in at -589 nT and the 1921 storm was probably on a similar scale.

What frightened the solar scientists was that the July 2012 storm would have had a Dst index of up to -1,200 nT if it had struck Earth, making it much worse than the Carrington Event.

Scientists are able to analyse the July 2012 storm in detail because although it was angled away from Earth it made a direct hit on a solar observation satellite, STEREO-A, which is specially hardened to withstand extreme magnetic disturbances.

But had it hit Earth, it would have done severe damage to power grids and satellite communications.

RISK MANAGEMENT

Severe solar storms occur much more often than previously thought.

Like many natural phenomena, the frequency with which solar storms take place scales as an inverse power of the severity of the event. But the sheer number of large storms over the last 150 years suggests the Carrington Event is unlikely to be an isolated occurrence.

Calculations by solar scientist Pete Riley, at Predictive Science Inc, suggest the probability of a solar storm of at least the power of the Carrington Event hitting Earth in the next 10 years is around 12 percent ("On the probability of occurrence of extreme space weather events", February 2012).

While not high, a 12 percent probability hardly qualifies as a "low-frequency" or remote-probability event.

So it is essential that the power industry and policymakers better understand how it would impact vulnerable systems (including the grid, global positioning system, radio and television communications, satellites and aircraft), harden them where possible, and plan how to cope with the aftermath of a big storm.

Once a large flare is detected, the industry and policymakers would have just an hour or so to put the grid and other systems into the safest possible operating mode before the storm arrives. - Reuters

* The opinions expressed here are those of the author, a columnist for Reuters




Tags: | Earth | Solar storm |

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