(The opinions expressed here are those of the author, a
columnist for Reuters)
By John Kemp
LONDON, July 25 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
percent, 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 (1,500 miles) 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," U.S. solar
researchers warned in the journal Space Weather ("A major solar
eruptive event in July 2012: defining extreme space weather
scenarios", October 2013).
"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 U.S. 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 U.S. 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 U.S. 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 Sept. 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
U.S. 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.
PRIOR PREPARATION
Before the next major storm arrives, it is essential to
understand which transformers and other equipment are most at
risk.
Policymakers must consider whether to replace, redesign or
otherwise harden the most at-risk equipment to withstand the
impact.
It is also essential to identify how the grid (and other
systems) could be rendered as safe as possible before the storm
strikes.
Readying the grid could involve turning the power to
customers down or off to reduce the loading on critical
transformers and make them less vulnerable to overheating.
If power and communications systems are likely to be
disrupted, businesses, households and government agencies will
need to be informed quickly.
And once the storm has passed, grid operators and
policymakers must have a plan for damage repairs.
Grid managers already plan how to re-energise the grid after
large-scale blackouts such as the one that hit the northeast
United States and neighbouring parts of Canada in August 2003.
The process is known as a "black start" and involves a
careful sequence of steps to restart power plants, re-energise
power lines and transformers, and gradually restore supplies.
But a severe solar storm might also cause more permanent
damage, so the industry needs to supplement its black start
procedure with a plan for handling multiple transformer outages.
Between 1996 and 2010, the SOHO satellite recorded almost
15,000 coronal mass ejections. It is only a matter of time
before one of them is aimed at Earth and is of the same
magnitude as Carrington, or worse.
Given the frequency of large solar storms, most people
reading this article will witness at least one.
And given society's increasing dependence on electricity and
electromagnetic communications, storms could do much more damage
in future, just one way in which new vulnerabilities are
emerging in high-tech economies.
The biggest threat is probably in emerging markets,
especially middle-income countries, where the combination of
widespread electrification and electronic communications coupled
with outdated and overloaded equipment makes them especially
vulnerable.
But even in the most advanced economies, a severe solar
storm could leave homes and businesses without power for months.
Proper risk management and preparation are therefore essential.
We cannot stop a big solar storm arriving, but we can
prepare and try to avoid its worst effects.
(Editing by Dale Hudson)