NASA satellite fleet figures out why Northern Lights dance

The great, colorful  Northern Lights that eerily appear in the winter sky are caused by magnetic energy located a third of the way to the moon, NASA said today.

"We discovered what makes the Northern Lights dance," said Dr. Vassilis Angelopoulos of  the University of California, Los Angeles. Angelopoulos is the principal investigator for the Time History of Events and Macroscale Interactions during Substorms mission (THEMIS).   THEMIS is NASA's 2-year mission consisting of 5 satellites that will study the violent colorful eruptions of Auroras.

According to NASA, just as hail and tornadoes accompany the most severe thunderstorms, substorms accompany the most intense space storms - those that disrupt communications, cause power line transmission failures, and produce the most penetrating radiation.

It is these substorms produce changes in the auroral displays seen near Earth's northern and southern magnetic poles, causing a burst of light and movement in the Northern and Southern Lights also known as aurora borealis.

According to NASA, scientists observe the beginning of substorms using  the five THEMIS satellites and a network of 20 ground observatories located throughout Canada and Alaska.

Launched in February 2007, the five identical satellites lined up once every four days along the equator and take observations synchronized with the ground observatories. Each ground station used a magnetometer and a camera pointed upward to determine where and when an auroral substorm will begin. Instruments measured the auroral light from particles flowing along Earth's magnetic field and the electrical currents these particles generate.

During each alignment, the satellites captured data that let scientists precisely pinpoint where, when, and how substorms measured on the ground develop in space, NASA said.

"As they capture and store energy from the solar wind, the Earth's magnetic field lines stretch far out into space. Magnetic reconnection releases the energy stored within these stretched magnetic field lines, flinging charged particles back toward the Earth's atmosphere," said David Sibeck, THEMIS project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. In a release. "They create halos of shimmering aurora circling the northern and southern poles."

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