Astronomy Picture of the Day



Green and Black Aurora Over Norway

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#85477 by @ 30.03.2006 00:00 - nach oben -
Green and Black Aurora Over Norway


Explanation:
What causes gaps between aurora curtains?

These unusual gaps can make
auroral displays appear more detailed and intricate.

Research using data from four
Cluster spacecraft orbiting the Earth has likely found the secret:
auroral gaps, sometimes knows as black auroras, are actually anti-auroras.

In normal auroras,
electrons and/or predominantly negatively charged
particles fall toward Earth along surfaces of constant
magnetic field.

They ionize the
Earth's atmosphere on impact, causing the bright glows.

In auroral gaps, however, negatively charged particles may be sucked out
from the Earth's
ionosphere
along adjoining
magnetic field lines.

These
dark anti-auroras can climb to over 20,000 kilometers
and last for several minutes.

Pictured above, a series of well-defined
auroral gaps is seen dividing green aurora curtains high above
Harstad,
Norway, earlier this month.




News: Solar Eclipse Today



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