Aurorae in Iceland

4th April, 2019

“It was the best of tripods, it was the worst of tripods”. Jane patiently took these aurora pictures at 10:00 pm last night with her back hard against the metal of a cold, cold car to steady the camera. After nearly three months patiently watching and hoping, we finally got to see aurorae against a cloudless sky.

We had spent the evening working through YouTube videos and technical articles, learning how to configure manual F-stops, ISO settings and shutter speeds on her Canon ES600D camera. Automatic camera settings cannot capture night-time images like these. The sky had been empty but at about 9:45 pm I saw a glimmer out the window. Going outside, the sky on the other side of the building was alive…

What is an aurora?

The aurora is seen as a luminous glow that appears around the magnetic poles of the Northern and Southern hemispheres. Electrically charged particles streaming out from the sun as the Solar Wind enter the Earth’s atmosphere, colliding with oxygen and nitrogen molecules. During these collisions, the particles gain energy. As they drop back to their normal state, that energy is released as visible light.

The dancing lights of the aurora appear only around the magnetic poles of the Northern and Southern hemispheres because the Solar Wind electrons travel along magnetic field lines in the Earth’s magnetosphere. The green oval shown in the diagram above defines the viewable area where the aurora can be seen.

The magnetosphere is a vast, comet-shaped bubble around our planet. As the electrons from the solar wind penetrate into the upper atmosphere, the chance of colliding with an atom or molecule increases the deeper into the atmosphere they go. Oxygen at about 90 kilometers up gives off the familiar green-yellow color, oxygen at higher altitudes above km gives all-red auroras. Nitrogen in different forms produces the blue and red-purple light. The green oval shown in the diagram above defines the viewable area where the aurora can be seen.

Earth is probably unique in the Solar System. Mars has no magnetic field, atmospheric oxygen or nitrogen so it is unlikely that aurorae could be seen there. Venus has a thick atmosphere that would prevent aurorae being seen.