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Solar storms pose risk to technology
The solar storm that grazed the Earth last week, disrupting communications across parts of the Northern Hemipshere, was caused by the most powerful solar flare to reach us in four years.

But scientists say the flare, which created a huge coronal mass ejection, was mild compared to what we might see in the near future.

Dr Dave Neudegg of Australia's Ionospheric Prediction Service (IPS) says we're currently on the upswing of the 11-year sunspot cycle.

"We're coming out of a very long, deep solar minimum," he says.

"This is one of the first significant sunspot regions for about the last four years, and the number of sunspots will keep going up until we get to solar maximum in about 2013-14. So you'll get more of these shockwaves and more of these magnetic storms on the earth."

Some solar flares punch out a coronal mass ejection (CME), basically a ball of superheated ionised gas, or plasma, containing protons and electrons. The energy in the solar flare, in the form of radiation, reaches Earth first.

In last week's flare and CME, China took the initial brunt, when a burst of x-ray radiation knocked out shortwave radio communications.

"Basically when the big x-ray flare happens, the x-rays just travel like light, straight to the Earth in eight minutes," Neudegg says.

Two days later, a CME bombarded the Earth's magnetic field with a wave of charged plasma. That widely disrupted satellite communications and the global positioning system (GPS).

Neudegg describes a CME as being like a shockwave in air, with an added magnetic component. He says the Sun's magnetic field goes out through the solar system [with the CME] and interacts with the Earth's magnetic field about 50,000 kilometres up.
Electricity grid failures

"If you get a really big shockwave hitting the geomagnetic field the interaction between the magnetic fields sends electric currents down to Earth," Neudegg says.

"They try to flow through the Earth. But if they can find something more conductive, like a power grid, then they'll go through that. The longer the grid, the more likely that is, so you get a current surge and it knocks out transformers. That happened two solar maximums ago in Canada, in Quebec."

On 13 March 1989, a CME caused a power surge through Quebec's electricity grid. Much of the grid was up and running nine hours later, but some areas were without power for days.

Neudegg says that governments around the world have been working on contingency plans and that IPS has been helping Australian electricity providers to be ready for such an event.

"In Australia if it's a really large event they consider separating all the state grids for a few hours to minimise the chance of that happening," he says. "You'd need a very big event for that to happen."

Neudegg says that as we've become more dependent on technology, the potential ramifications of CMEs get worse.

"A really famous large event is what they call the Carrington event in 1859," he says. "The electric telegraph was the only technology affected, but the current flowing through the lines made them so hot that the paper caught fire in the telegraphs."

The fact that these days global communications are more and more reliant on satellites sitting about 36,000 kilometres out into the magnetosphere.

"A significant number would probably get knocked out," says Neudegg.

Professor Andrew Dempster, Director of the Australian Centre for Space Engineering Research (ACSER) at the University of New South Wales, says the higher a satellite is, the more vulnerable it is to solar radiation.

"Communications satellites at 36,000 kilometres are slightly more affected than GPS at 26,000 kilometres. They in turn are much more vulnerable than Earth observation satellites which are only hundreds of kilometres up."
Satellites falling from orbit

He says GPS errors get worse when there are disturbances in the ionosphere.

"GPS measures distance from the satellites to the receiver. As the signal passes through the ionosphere, it's delayed by an amount proportional to the 'free electron count'," says Dempster.

"This delay introduces an error into the range measurement. Solar radiation affects this free electron count, making the error larger and less predictable."

While this may be inconvenient for those with smartphones or in-car GPS receivers, it becomes much more serious for shipping, civil aviation and the military.

Associate Professor Michael Wheatland from the School of Physics University of Sydney says solar flares pose other problems for low orbit satellites.

"Like Skylab falling to Earth in 1979," he says. "Those satellites that are closer to the Earth experience drag from the Earth's atmosphere. Then when you get this increased radiation due to flares, the atmosphere swells and it slows them down even more and they eventually fall back down to Earth."

Scientists still can't predict accurately when solar geomagnetic storms will hit, beyond two or three days in advance.

But according to Neudegg, the number and severity of these events is likely to increase.

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