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Solar Storms: Impact of a Coronal Mass Ejection

This story is a supplement to the feature "Bracing the Satellite Infrastructure for a Solar Superstorm" which was printed in the August 2008 issue of Scientific American.

Normal Conditions:
Earth’s magnetic field typically deflects the charged particles streaming out from the sun, carving out a teardrop-shaped volume known as the magnetosphere. On the sun-facing side, the boundary, or magnetopause, is about 60,000 kilometers from our planet. The field also traps particles in a doughnut-shaped region known as the Van Allen belts.

First Stages of Impact:
When the sun fires off a coronal mass ejection (CME), this bubble of ionized gas greatly compresses the magnetosphere. In extreme cases such as superstorms, it can push the magnetopause into the Van Allen belts and wipe them out.

Magnetic Reconnection:
The solar gas has its own magnetic field, and as it streams past our planet, it stirs up turbulence in Earth’s magnetic field. If this field points in the opposite direction as Earth’s, the two can link up, or reconnect—releasing magnetic energy that accelerates particles and thereby creates bright auroras and powerful electric currents.

Illustrations by Melissa Thomas

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