Solar Storms

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Craig DeForest is a solar physicist at the Southwest Research Institute.

Zap! Pow! Giant storms sweep through outer space!

On October 28, 2003, part of the Sun exploded, giving rise to the third largest solar flare ever recorded. The explosion released energy equivalent to that produced by more than a billion 1-megaton nuclear bombs. As a minor side effect, more than a kilogram of antimatter was formed in the explosion and detonated a few seconds later on the Sun's surface. In addition, several billion tons of superhot plasma were hurled outward at nearly four million miles per hour, zooming across the solar system to impact Earth 24 hours later.

On November 4, the Sun flared again, with two important differences. The later flare was over five times more powerful. And it happened to be pointed away from Earth, so the cloud missed us. Humanity got lucky when the "perfect space storm" passed us by.

Solar flares have been giving off bursts of radiation, and coronal mass ejections (CMEs) have been flying from the Sun, for most of the solar system's 4.6-billion-year history. But only in the past few years have scientists begun to understand the complex relationship between solar flares, CMEs, and our planet. Solar flares are the largest explosions in the solar system, but their main impact on Earth comes from CMEs, large clouds of material that are flung across the solar system by flares and some other types of solar events.

Earth's surface is well shielded from them by both our planet's magnetic field and its atmosphere, so we are not affected directly. But our modern technology is increasingly vulnerable to "space weather" caused by both types of event. For the first time, our current fleet of Sun- observing and Earth-observing spacecraft is giving a complete picture of the whole process and allowing us to understand, predict, and avoid the worst effects.

Like many CMEs before it, the speeding cloud from the October 28 flare was diverted around our planet by Earth's magnetic field, but at a cost. Our magnetic field temporarily recoiled, inducing large current spikes in the world's electrical power grids, threatening spacecraft, and interfering with radio communications, cell phones, and pagers. The famous Van Allen radiation belts were squeezed toward the planet. In the middle latitudes, accelerated particles shot down from the boundary of deep space to slam into our atmosphere, lighting it up like a neon tube with a brilliant, beautiful aurora.

As early as 1905, the aurora was been linked to mysterious over-voltage problems on European telegraph lines. We now know that long wires, such as are used to carry telephone and power signals, act as simple electrical generators when the magnetic field around Earth changes …