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NASA Satellites Discover What Powers Northern Lights

Written by thomas · Filed Under Aeronautics News 

July 24, 2008

thomas

GREENBELT, Md., July 24 /PRNewswire-USNewswire/ — Researchers using a
fleet of five NASA satellites have discovered that explosions of magnetic
energy a third of the way to the moon power substorms that cause 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.

“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, or THEMIS.

Substorms produce dynamic 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.

Substorms often accompany intense space storms that can disrupt radio
communications and global positioning system signals and cause power
outages. Solving the mystery of where, when, and how substorms occur will
allow scientists to construct more realistic substorm models and better
predict a magnetic storm’s intensity and effects.

“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. “They create halos of shimmering aurora circling the
northern and southern poles.”

Scientists directly observe the beginning of substorms using five
THEMIS satellites and a network of 20 ground observatories located
throughout Canada and Alaska. Launched in February 2007, the five identical
satellites line up once every four days along the equator and take
observations synchronized with the ground observatories. Each ground
station uses a magnetometer and a camera pointed upward to determine where
and when an auroral substorm will begin. Instruments measure the auroral
light from particles flowing along Earth’s magnetic field and the
electrical currents these particles generate.

During each alignment, the satellites capture data that allow
scientists to precisely pinpoint where, when, and how substorms measured on
the ground develop in space. On Feb. 26, 2008, during one such THEMIS
lineup, the satellites observed an isolated substorm begin in space, while
the ground-based observatories recorded the intense auroral brightening and
space currents over North America.

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.

THEMIS is the fifth medium-class mission under NASA’s Explorer Program.
The program, managed by the Explorers Program Office at Goddard provides
frequent flight opportunities for world-class space investigations in
heliophysics and astrophysics. The University of California, Berkeley’s
Space Sciences Laboratory in Berkeley, Calif., managed the project
development and is currently operating the THEMIS mission. ATK Space
(formerly Swales Aerospace) of Beltsville, Md., built the THEMIS
satellites.

The THEMIS team’s findings will appear online July 24 in Science
Express and Aug. 14 in the journal science. For more information about the
THEMIS mission, visit:

http://www.nasa.gov/themis

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