Arctic-Color

Norrsken

There is nothing else in the sky to compare to the northern lights. The sun, moon, stars and planets are stable, predictable. The northern lights are variable, transient. Colours and movements unique in nature. Photographs are still images of an overwhelming phenomenon. My one wish is that every person that is interested in this incredible performance of nature should see for themselves, even if just once, the dancing display of the northern lights on a clear autumn or winter night

What are northern lights ?
Northern lights are part of a process, a reaction between the solar wind and the earths magnetic field. There are sources on the sun that give off charged particles; electrons and positive ions at different speeds. This is known as plasma. This spray of super hot ionized gas blows across spay as the solar wind.

The sun is a huge magnet with its own force field stretching far beyond it. This gets twisted into a spiral by the suns; rotation and within this spiral the particles travel along the magnetic field lines. The solar winds now head towards the earth at several hundred miles per second and hit the edge of our own magnetic sheath: the magnetosphere. Like water hitting a solid object, the solar winds goes past the earth but pushes in again on the night side, squeezing the magnetosphere and elongating it into a comet shaped tail.

The solar winds continue to travel along the earths magnetic field collecting particles which originate in the earths atmosphere. The electrical particles move along the magnetic field and reach farthest down into the atmosphere in the Polar Regions. The concentration of particles is found in a halo or ring round both poles. The aurora borealis in the Northern Hemisphere and one for the mirroring aurora australis in the Southern Hemisphere. Until now there has been no light or colour so what happens next?

Why the colors of northern lights ?
As the electrons fall into the ionosphere they collide with particles already there. Primarily it is oxygen and nitrogen but also present is helium, hydrogen, neon and argon. As a result of this collision the oxygen atoms and nitrogen molecules acquire extra energy. They become excited and leave their ground state for a very short time. They do not want this extra energy and want to get rid of it almost immediately. They emit it as photons. This is the light we see.

The atmosphere is too dense for particles to penetrate low down at around an altitude of 90 kms. This height defines the lower edge of the northern lights. Correspondingly, the first collision may occur at an altitude of 1000 kms, which is the maximum altitude of the upper edge. However normally the northern lights appear at around 100/200 kms. Rainbows contain all the colours of the spectrum. The northern lights show only individual colours. The most intensive colours are yellowish green through to different hues of red. Generally oxygen atoms that are hit emit the yellow / green colour which is the easiest for the human eye to see. Oxygen also makes the deep red colour at the upper edge of the northern lights. Nitrogen will emit the bluish red lower edge of many arcs and is also responsible for the blue and violet colours that are often more difficult for the human eye to see. I have often been surprised at the results of some photographs because the film has captured blue and violet colours which my eye has not seen but the camera has captured. So when photographing northern lights I never am totally sure of what the results will be. The unpredictable showers of electric particles give the northern lights their forms and movements. Arcs, draperies, rays, spirals, coronas.

Where to see the northern lights ?
I am fortunate to live in one of the areas with a high probability of seeing and thus photographing northern lights. For me, this is from late August to early April. The auroral zones are at a distance of 200/300 kms from the poles. The zones themselves around a couple of hundred kilometers wide. The auroral light forms almost a circular shaped oval. So from the ground we can see part of this oval at night as northern lights in the sky. The lights seen in the northern hemisphere and the southern hemisphere are a mirror image of each other as regards shape of the aurora. This is caused by the symmetry of the magnetic field.

Photographing northern lights
Science says that Scandinavia is probably under this oval at magnetic midnight which occurs at about 22-22.30. I am sure this must be true but I can also add that after many observances of the northern lights I have photographed many at 16.00-20.00 during November and December and very many around 20.00-22.00 at other times of activity. So if you are searching to see the aurora, be prepared to be looking all the time it is dark !

To photograph northern lights I have one camera set ready at all times. I use a canon T90 with a 55 mm 1.2 lens. Occasionally I have a second camera, canon EOS 5 with 20mm 2.8 lens. I have found there are no ‘rules‘ for photographing northern light. It depends on your camera lens, film, the intensity of the display. When using the T90 with 55mm 1.2 lens and 400 asa film I will expose frames from 30th second to 10 seconds. When using EOS 5 with 20mm lens and 400 asa film I will expose from 5-20 seconds. If the film speed changes, the expose time changes to correspond. This means every night of photographing the lights is a different experience. No two displays are ever the same and no two pictures are ever identical. It is exciting and frightening to wait for the results !

Natures Light Show
Whatever myths abound, whatever one believes, whatever science suggests about northern lights to me it is the most awesome phenomenon I have ever seen. Sometimes the displays are so overwhelming, so energetic, and so colourful it defies one to capture even a part of it on film. On those occasions I simply lie on my back in the snow and watch in awe and enjoy “Natures Light Show“.