Northern Lights Mystery Exposed

July 24, 2008 -- Scientists have exposed some of the mystery behind the northern lights. On Thursday, NASA released findings that indicate magnetic explosions about one-third of the way to the moon cause the northern lights, or Aurora Borealis, to burst in spectacular shapes and colors, and dance across the sky.

The findings should help scientists better understand the more powerful but less common geomagnetic storms that can knock out satellites, harm astronauts in orbit and disrupt power and communications on Earth, scientists said.

A fleet of five small satellites, called Themis, observed the beginning of a geomagnetic storm in February, while ground observatories in Canada and Alaska recorded the brightening of the northern lights. The southern lights -- aurora australis -- also brightened and darted across the sky at the same time.

These auroral flare-ups occur every two or three days, on average.

A team led by University of California, Los Angeles, scientist Vassilis Angelopoulos confirmed that the observed storm about 80,000 miles from Earth was triggered by a phenomenon known as magnetic reconnection. Every so often, the Earth's magnetic field lines are stretched like rubber bands by solar energy, snap, are thrown back to Earth and reconnect, in effect creating a short circuit.

It's this stored-up energy that powers the northern and southern lights or, in other words, causes them to dance, according to Angelopoulos.