Encore - Green Aurora Over Orsta, Norway
August 15, 2015
Take a look back at some of the EPODs our viewers found particularly eye-catching. Today, and every Saturday EPOD invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers’ Choice polls. Join us as we look back at these intriguing and captivating images.
The photo above shows a display of brilliant northern lights as viewed above the Sunnmøre Alps of Norway on January 20, 2010. Intense greenish bands dancing across the northern sky were obvious much of the night. There’s been a dearth of aurora in recent months, corresponding to a noticeable reduction of solar activity and a paucity of sunspots. Auroras result when very high speed particles from the Sun, known as the solar wind, bombard the Earth’s upper atmosphere (magnetosphere). Primarily electrons, these energetic particles are guided along magnetic field lines toward both the north and south magnetic poles where they collide with air molecules. When the molecules or air particles recombine, light is emitted. The green colors are due to emission of atomic oxygen in the green portion (530 nanometers) of the visible spectrum. The red coloration above the horizon is perhaps from auroral light shining through the cloud deck. There are no city lights or artificial lighting in the direction the camera is facing.
Photo details: Canon EOS 450D camera, tripod and remote controller, Sigma 17-70 mm lens (set to 25 mm), ISO 800, exposure time 18 seconds.
Coordinates for Orsta, Norway: 62.23056, 6.31694
EPOD for December 17, 2005 - Sunnmøre Alps of Norway