NASA's new THEMIS, a five-satellite constellation that takes data on the earth's magnetosphere, has provided evidence that these substorms come from shifts and re-connections of the disturbed magnetosphere, far out from the planet.
Researchers have discovered that an explosion of magnetic energy a third of the way to the moon powers substorms, sudden brightenings and rapid movements of the aurora borealis, called the Northern Lights.
The culprit turns out to be magnetic reconnection, a common process that occurs throughout the universe when stressed magnetic field lines suddenly "snap" to a new shape, like a rubber band that's been stretched too far.
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These observations confirm for the first time that magnetic reconnection triggers the onset of substorms. The discovery supports the reconnection model of substorms, which asserts a substorm starting to occur follows a particular pattern. This pattern consists of a period of reconnection, followed by rapid auroral brightening and rapid expansion of the aurora toward the poles. This culminates in a redistribution of the electrical currents flowing in space around Earth.