s at hand. More exact explanations of the phenomenon could not be given until modern particle physics were developed, and knowledge about details in the earths magnetosphere 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 outbursts starts with a phosphorocent glow over the horizon in north west. 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. (Picture 1).
             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 auroral sub-storm. Rays o
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