One of the great attractions of Finland is the chance to experience the Northern Lights, or Aurora Borealis, and every year thousands of visitors come here to see them.
Although the best place to see them is the Kilpisjärvi region, in Lapland, the Aurora Borealis can also be seen as far south as Helsinki. In fact there are about 20 days in a year when the lights can be seen in Southern Finland, the main problem being the high levels of light pollution and the difficulty in finding dimly lit areas. As one would expect, this is not an issue in Lapland, where the lack of city lights ensures that there are some 200 nightly occurences every year.
The best times of the year for viewing this incredible spectacle are obviously during the dark winter months, and other peak seasons are September through October, and February through March. In the Kilpisjärvi region, on clear nights during the dark period of the year, the auroras can be seen 3 nights out of every 4 on average. Further north, at Utsjoki for example, there is a decrease of 10%, and likewise as you travel further south the incidence also decreases. In the Sodankylä region you can see the auroras every second night on average, and in the Oulu-Kuusamo region every fourth night.
The best time of the night to see the Northern Lights is usually between 9pm and 11.30pm when they peak. This is due to the magnetic midnight and the fact that the disturbances in the Earth's magnetic field are at a maximum. After midnight the incidence of the lights begins to diminish, and by 4am to 5am the probablity of occurrence falls below 50%.
So what are these ghostly lights in the sky? Finns refer to them as 'revontulet' which means foxes fire, and refers to a Sami, or Lapp, legend that the aurora was caused by a fox running along the snow-covered fells striking its tail on the snowdrifts and sending trails of sparks into the sky. Other northern peoples believed the aurora came from the blood of the dead, blood that ran when the spirits played ball or rode horses in the afterlife. Yet another legend would have it that the auroras are really Thor throwing thunderbolts at Väinämöinen, the hero of the great Finnish epic, The Kalevala. In fact, from Siberia to Scotland and across the great plains of America, every culture that has experienced these wondrous lights has developed their own mythology to describe it, and there are nearly as many myths surrounding the Aurora Borealis as there are for the Sun and the Moon.
Science has provided us with an explanation no less beautiful. The Northern Lights are largely caused by solar flares, which create the solar storms and solar winds that buffet our planet. As electrons are blown by the solar winds they collide with molecules in the ionosphere, creating electromagnetic radiation whose spectrum ranges from infrared to ultraviolet. The visible spectrum is mostly white and green light produced by oxygen molecules in a state of excitement, and pink light which is emitted from nitrogen.