Scientists learn what makes Northern Lights flare
WASHINGTON, July 24 (Reuters) - The multicolored aurora
borealis and aurora australis -- the Northern Lights and
Southern Lights -- represent some of Earth's most dazzling
natural displays.
Now scientists using data from five NASA satellites have
learned what causes frequent auroral flare-ups that make this
green, red and purple lightshow that shimmers above Earth's
northernmost and southernmost regions even more spectacular.
Writing in the journal Science, the scientists said on
Thursday that explosions of magnetic energy occurring a third
of the way between Earth and the moon drive the sudden
brightening of the Northern Lights and Southern Lights.
There had been debate among scientists dating back decades
about what triggers these auroral flare-ups.
The findings from the THEMIS satellites and a network of 20
ground observatories in Canada and Alaska confirmed that it is
due to a process called "magnetic reconnection." THEMIS stands
for Time History of Events and Macroscale Interactions during
Substorms mission.
Auroral displays are associated with the solar wind --
electrically charged particles continuously spewing outward
from the sun. Earth's magnetic field lines reach far out into
space as they store energy from the solar wind.
The researchers said that as two magnetic field lines come
close together due to the storage of energy from the sun, a
critical limit is reached and the lines reconnect, causing
magnetic energy to be turned into kinetic energy and heat. The
release of this energy sparks the auroral flare-ups.
"We showed that the process begins far from Earth first and
propagates Earthward later," said Vassilis Angelopoulos of the
University of California at Los Angeles, who led the research.
The moon is located about 240,000 miles (385,000 km) from
Earth, and this process is occurring roughly 80,000 miles
(128,000 km) from Earth.
The same mechanism causing the auroral brightening also can
cause problems for satellites, power grids and communications
systems on Earth and could endanger astronauts in space, the
researchers said.