Aurora Over Southern Finland
December 17, 2015
Photographer: Niko Laurila
The photo above shows a striking green aurora observed over Porvoo, Finland on the night of December 14, 2004. At approximately 10:00 p.m. I noticed a nocturnal glow to the north and grabbed my camera. Auroras result when oxygen atoms, and also nitrogen atoms, are excited by charged particles emanating from solar flares. Green auroras tend to form about 60 - 160 mi (100 - 250 km) above the Earth's surface when the excited oxygen atoms return to their original unexcited state. The emission of this light is centered at a wavelength of 558 nanometers -- in the green portion of the electromagnetic spectrum.
Photo Details: Camera Model: NIKON D610; Lens: 14.0-24.0 mm f/2.8; Focal Length: 15mm (35mm equivalent: 15mm); Aperture: ƒ/2.8; Exposure Time: 5.000 s; ISO equiv: 800; Software: Adobe Photoshop CC (Windows).