Explosions of magnetic energy between Earth and the moon are behind the sparkles and wavy glows of the Northern Lights that color the night sky, Nasa said on Thursday.
A network of five satellites of a mission known as THEMIS that studied the phenomenon for a year helped researchers lift the veil from some of the mystery behind the aurora borealis.
"We discovered what makes the Northern Lights dance," said Vassilis Angelopoulos of the University of California, Los Angeles, the principal investigator for the THEMIS mission, which stands for Time History of Events and Macroscale Interactions during Substorms.
The energy explosions that take place a third of the way between Earth and the moon power the substorms that cause the sudden brightening and rapid movements of the northern lights, researchers said.
Substorms are triggered by magnetic reconnection, a common process that occurs throughout the universe when stressed magnetic field lines suddenly snap to a new shape, like an overstretched rubber band.
"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, Maryland.
"They create halos of shimmering aurora circling the northern and southern poles," he said.
Magnetic energy blasts make Northern Lights 'dance'