In English

Lapland is one of the best regions in the world for spotting aurora borealis, the northern lights

Northern Finland is one of the best regions in the world for spotting aurora borealis, the northern lights. In Saariselkä, Inari and Utsjoki you can see the northern lights on three to four nights a week.

Observing the northern lights is mostly hampered by cloud cover and other weather phenomena as well as by lights from urban areas and traffic. The northern lights are visible more or less uniformly throughout the year, but they are somewhat more common in autumn and spring than in winter and summer. In the summer the nights are too light, especially in the more southern parts of the country, for spotting the dim glow of the northern lights.

The occurrence of the northern lights also varies from year to year. It is not possible to predict their occurrence in any reliable manner.

A couple of hours before and after midnight

The most typical time for the occurrence of the northern lights is a couple of hours before and after midnight. You can, however, spot them sporadically all through the night. During major geomagnetic storms they may glow intensely from sunset to sunrise.

The weather does not affect the occurrence of the northern lights, but since the northern lights originate above all cloud formations, you cannot see them if the sky is covered by thick clouds.

If you wish to watch the northern lights, it is a good idea to seek an open place which is as dark as possible, away from light pollution.

A clear and dark night is good weather for watching the northern lights. You also need some patience if you wish to see the best of the northern lights. You should therefore make sure your clothes are sufficiently warm.

For example, lying on a sleeping pad may be a more comfortable approach to watching the sky than bending your neck upwards continuously.

Let your eyes take their time to adapt to the darkness. It takes a long time before your night vision is at its best. If you need an electric torch, only use dim red light, which will not impair your night vision.

The human eye is not particularly good at colour separation when it is dark. That is why the northern lights appear more faded to the naked eye than in photographs.

Energy from the sun

The northern lights originally get their energy from the sun even though they themselves originate in the upper atmosphere of the Earth at an altitude of some 100 to 200 kilometres.

The occurrence of the northern lights is regulated by sunspots. The sun continuously emits particles into the surrounding space. Particles from this current known as the solar wind also end up in the atmosphere of the Earth. There the process generating the northern lights is essentially the same as the one in a fluorescent tube. In the ionosphere, electrons dashing down in the magnetic field of the Earth collide with oxygen and nitrogen atoms, which momentarily become excited for a higher energy state. As the excited state dissipates, the excitation energy is released as a photon, that is, as light.

The speed of the particles falling into the upper atmosphere may be high as 1,000 kilometres per second. As the excited states dissipate, the colour of the light generated depends on the type of the excited particle and the energy it receives on impact: the excited states of oxygen atoms produce green and red light whereas nitrogen molecules receive and release energy in the amount of a bluish light quantum.

The flaming of the northern lights also varies by the time of the day. In the evening at 9 pm (Finnish winter time) the average likelihood for their occurrence in Lapland exceeds 50%. It reaches its high point approximately at 11.30 pm.

Tarja Karjalainen