for National Geographic News
A quintet of space probes will be launched next month to solve a decades-long mystery about auroras in Earth's atmosphere, NASA officials announced yesterday.
The probes will search for the origin of magnetic storms that cause auroras in the planet's Northern Hemisphere to change from slowly shimmering curtains of light into dancing streaks of briliant color.
Pinpointing when and where the storms originate will also enable researchers to better predict space weather.
In addition to lighting up the polar night, severe magnetic storms can disrupt spacecraft, radio communication, global positioning systems, and power transmission (related news: "Global Warming Could Disrupt GPS Satellites, Study Says" [November 29, 2006]).
The new mission "is a stepping stone toward understanding space weather phenomena that affect our lives," Vassilis Angelopoulos, principal investigator of the project at the University of California, Berkeley's Space Sciences Laboratory, told reporters yesterday.
Charged particles emanating from the sun are the ultimate source of auroras.
When these particles pass near Earth, they flow around the planet's magnetic field lines.
But some of the particles leak into Earth's magnetosphere and collide with air molecules. The impact releases visible light, creating an aurora.
Sometimes a severe magnetic storm can cause energy to build up until Earth's magnetic field breaks. This releases a sudden burst of high-speed electrons—a geomagnetic substorm.
The substorm makes a normally green aurora ripple and turn red, purple, and white.
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