Physics Photo of the Week

Warren Wilson College

November 12, 2004

Aurora photo by Simon Johnson
Auroras (northern lights) are very rare in North Carolina, but on Sunday night, November 7, 2004, members of Astronomy class on a field trip to the Blue Ridge Parkway, happened to be greeted by this magnificent display of Aurora Borealis at about  8:00 pm.   This was viewed from Craggy Pinnacle Parking Area, elevation approx. 5700 feet above sea level.  This same auroral display was seen from parts of Warren Wilson College campus.

The aurora is caused by energic electrons and protons emitted by the sun and intercepting the earth's
upper atmosphere.  The solar wind of these electrons and protons are strongly affected by the magnetic fields of the planets.  The earth's magnetic field usually deflects the charged particles toward the earth's magnetic poles (near the north and south poles) where auroral displays are almost constant.  Occasionally, a stronger concentration of charged particles is released from the sun (solar flares, sunspots, etc).  This "solar storm" creates an unusually large "auroral storm" and the auroras move to more mid-latitudes on the earth.  Notice the vertical streamers in the Simon's photo.  These vertical streamers are aligned with the earth's magnetic field which is about 50 deg to the horizontal at mid latitudes.  The red glow is generally from atomic oxygen in the earth's upper atmosphere, and the green arc is most likely due to nitrogen being excited by the energetic electrons.

Simon photographed the aurora above with a 15 sec time exposure, resting his camera on a stationary object.  No tripod was available.  The view is looking toward the northeast.  The bright star in the upper right is Capella.




Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to dcollins@warren-wilson.edu.

Click here to see all Physics Photo of the Week for 2004.