NASA Astronomy Picture of the Day Collection

Green and Black Aurora Over Norway

What causes gaps between aurora curtains? These unusual gaps can make auroral displays [ http://antwrp.gsfc.…] appear more detailed and intricate. Research [ http://sci.esa.int/…] using data from four Cluster spacecraft [ http://sci.esa.int/…] orbiting the Earth has likely found the secret: auroral gaps, sometimes knows as black auroras [ http://www.phys.uca…], are actually anti-auroras. In normal auroras [ http://en.wikipedia. org/wiki/Aurora_(ast ronomy) ], electrons [ http://www-istp.gsf…] and/or predominantly negatively charged particles fall toward Earth along surfaces of constant magnetic field [ http://www-istp.gsf…]. They ionize [ http://www-istp.gsf…] the Earth's atmosphere [ http://liftoff.msfc…] on impact, causing the bright glows. In auroral gaps, however, negatively charged particles may be sucked out from the Earth's ionosphere [ http://www.haarp.al…] along adjoining magnetic field [ http://www-istp.gsf…] lines. These dark anti-auroras [ http://www.gi.alask…] can climb to over 20,000 kilometers and last for several minutes. Pictured above [ http://spaceweather…], a series of well-defined auroral gaps is seen dividing green aurora curtains high above Harstad [ http://en.wikipedia…], Norway [ http://en.wikipedia…], earlier this month.

//www.nettfoto.no/di verse/copyright-e.ht m" >Copyright: Frank Andreassen (nettfoto.no)

Alaska

Norway

Goddard Space Flight Center (GSFC)

Marshall Space Flight Center (MSFC)

Earth

Aurora

http://antwrp.gsfc.…

SPD-APOD-ap060329