How a solar flare could send us back to the Stone Age

A powerful enough solar flare could knock out our power grids, disrupt our GPS satellites, and bring the global economy to a halt, warns a British scientists.

A stream of highly charged particles from the sun is headed straight toward Earth, threatening to plunge cities around the world into darkness and bring the global economy screeching to a halt.

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This isn't the premise of the latest doomsday thriller. Massive solar storms have happened before ? and another one is likely to occur soon, according to Mike Hapgood, a space weather scientist at the Rutherford Appleton Laboratory near Oxford, England.

Much of the planet's electronic equipment, as well as orbiting satellites, have been built to withstand these periodic geomagnetic storms. But the world is still not prepared for a truly damaging solar storm, Hapgood argues in a recent commentary published in the journal Nature.

Hapgood talked with the Los Angeles Times about the potential effects of such a storm and how the world should prepare for it.

Q: What exactly is a solar storm?

A: I find that's hard to answer. The term "solar storm" has crept into our usage, but nobody has defined what it means. Whether a "solar storm" is happening on the sun or is referring to the effect on the Earth depends on who's talking.

I prefer "space weather," because it focuses our attention on the phenomena in space that travel from the sun to the Earth.

Q: People often talk about solar flares and solar storms in the same breath. What's the difference?

A: Solar flares mainly emit X-rays ? we also get radio waves from these things, and white light in the brightest of flares. They all travel at the same speed as light, so it takes eight minutes to arrive. There are some effects from flares, such as radio interference from the radio bursts.

But that's a pretty small-beer thing. The big thing is the geomagnetic storms (on Earth) that affect the power grid, and that's caused by the coronal mass ejections (from the sun).

Coronal mass ejections are caused when the magnetic field in the sun's atmosphere gets disrupted and then the plasma, the sun's hot ionized gas, erupts and send charged particles into space. Think of it like a hurricane ? is it headed toward us or not headed toward us? If we're lucky, it misses us.

Q: How are solar flares and coronal mass ejections related?

A: There's an association between flares and coronal mass ejections, but it's a relationship we don't quite understand scientifically. Sometimes the CME launches before the flare occurs, and vice versa.

Q: What happens when those particles reach Earth?

A: There can be a whole range of effects. The classic one everyone quotes is the effect on the power grid. A big geomagnetic storm can essentially put extra electric currents into the grid. If it gets bad enough, you can have a complete failure of the power grid ? it happened in Quebec back in 1989. If you've got that, then you've just got to get it back on again. But you could also damage the transformers, which would make it much harder to get the electric power back.

Q: How else could people be affected?

A: You get big disturbances in the Earth's upper atmosphere ? what we call the ionosphere ? and that could be very disruptive to things like GPS (the network of global positioning system satellites). Given the extent we use GPS in everyday life (including for cellphone networks, shipping safety and financial transaction records), that's a big issue.

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