Massive electric explosions between the Earth and the moon’s orbit create dazzling movements of the aurora borealis, researchers at UCLA and NASA Goddard Space Flight Center announced last week.

Using a fleet of five satellites manufactured by Beltsville’s ATK Mission Systems, researchers captured comprehensive maps of otherwise invisible electric substorms in space. The probes in the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission were launched on one rocket in February 2007, then deployed into oblong orbits stretching halfway to the moon. Every four days they line up in the Earth’ shadow, providing detailed information from different points in our magnetic tail.

“As they capture and store energy from the solar wind, Earth’s magnetic field lines stretch far out into space,” said David Sibeck, THEMIS project scientist at NASA’s Goddard Space Flight Center in Greenbelt. “Magnetic reconnection releases the energy stored within these stretched magnetic field lines, flinging charged particles back toward the Earth’s atmosphere.”

The team’s findings appeared online July 24 in Science Express and will be published Aug. 14 in the journal Science.

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“We discovered what makes the Northern Lights dance,” Dr. Vassilis Angelopoulos of the University of California, Los Angeles, principal investigator for THEMIS, said in a statement.

In addition to beautiful auroral displays, these substorms — the result of intense space storms — can disrupt radio communications and global positioning system signals and cause power outages on the ground.

HOW IT WORKS

Information from the satellites is coordinated with a network of 20 ground observatories located throughout Canada and Alaska that capture full-sky images of the aurora.

Each ground station uses a magnetometer 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.

This February, the satellites lined up just as an isolated substorm began in space, according to NASA. The ground-based observatories recorded the intense auroral brightening and space currents over North America.

These observations confirmed for the first time how magnetic reconnection triggers the onset of substorms.

THE BIGGER PICTURE

Several other  satellite and spacecraft are refining our knowledge of magnetic disturbances driven by the solar wind.

The twin STEREO craft launched in 2006 are orbiting the sun at different locations, providing three-dimensional images of solar activity, including massive solar flares that supercharge the solar winds. These views give scientists their first opportunity to gauge the speed of changes in the solar winds and perhaps predict their impacts on earth. Those craft were developed and are being operated by NASA Goddard Space Flight Center in Greenbelt.

On the daylight side of the Earth, Johns Hopkins Applied Physics Laboratory in Laurel is gathering data from the privately operated Iridium communications satellite network to measure how much electricity our atmosphere absorbs from the solar winds.

khille@baltimoreexaminer.com