The Northern Lights

The Northern lights are poetry, they are nature's light show, and they are quantum leaps in the oxygen atom. They are elementary particle physics, superstition, mythology and fairy tales. The northern lights have filled people with wonder and inspired artists; they have frightened people to think that the end is at hand. More exact explanations of the phenomenon could not be given until modern particle physics were developed, and knowledge about details in the earth’s magneto sphere has been based on measurements from satellites.

When the northern lights are seen over Tromsø, it happens in a set pattern, although this pattern varies considerably. The outburst starts with a phosphorocent glow over the horizon in northwest. The glow dies out and comes back, and then an arch is lit. It drifts up over in the sky. And new arches are lit and follow the first one. Small waves and curls move along the arches.

Then within a few minutes a dramatic change is seen in the sky. A hailstorm of particles hit the upper atmosphere in what is called an aurora sub-storm.

Rays of light shoot down from space, forming draperies, which spread, all over the sky. And they really remind us of draperies or curtains, which are flickering in the wind. And you can see a violet and a red trimming at the lower and upper ends. Or the colors are mixed all together, woven into each other. The curtains are disappearing and forming all over again by new rays of light shooting down from space. Above our head we cans see rays going out in all directions forming what is called an aurora corona. After 10 to 20 minutes the storm is over and the activity decreases. The bands are spread out, disintegrating in a diffuse light all over the sky. We can not see individual pockets of light, but the total effect is bright enough to enable us to make out details of the countryside around us. If we look very carefully, we can see the remains of the northern lights display as faint, pulsating flames. Clouds of light which is turned on and off regularly every

5 - 10 seconds as though by an electric light-switch. The natures own gigantic light show is over.

What causes the northern lights? To answer this, we start with the sun whose energy production is far from even and fluctuates on an 11-year cycle.

Maximum production coincides with high sunspot activity when processes on the sun's surface throw particles ...

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...ll over the sky.

7) Bands of northern lights one above the other, raising towards the zenith indicates that the sub storm is starting.

8) Rays of light shoot down from space tells about higher activity.

9) Draperies are formed with waves at the lower end.

10) Curls and waves wave along the draperies.

11) The draperies look as if they are flickering in the wind. Maximum activities close.

12) The interaction between the moving charged particles and the earth’s magnetic field creates a charging magnetic field. The particles stream down along the magnetic field lines.

13) Rays and draperies can die out in one place of the sky, and form at another. 14) During the maximum of a sub storm, the whole sky can be full of light.

15) An all-sky (fish eye) picture showing that the draperies are stretched from east to west, through zenith.

16) When the activity reaches Zenith, by an optical illusion, it seems like the rays stretch out in all directions above our heads. This form of the northern lights is called aurora corona.

Works Cited

http://www.uit.no/npt/nordlyset/nordlysbilder.en.html

http://www.uit.no/npt/nordlyset/

Way North Magazine, publication by Tromsø Museum.