Eerily white, spookily green or simply multicoloured: polar lights are mystical, but also beautiful. Attempts to explain the natural phenomenon in the past were equally ancient: an invisible god spewing fire with rage. Today we know that polar lights are created when some of the solar wind is not diverted past the Earth, but is driven along the magnetic field lines to the poles. When the plasma of the solar wind enters the upper layers of the Earth’s atmosphere, the gas molecules are excited to fluoresce – they glow. For a green aurora, as in the photo, oxygen atoms are excited a good 100 kilometres above the Earth’s surface. In northern Finland, up to 200 auroras can be seen each year. In the south of the country, around Helsinki, the natural phenomenon can be observed up to 20 times a year.
More information: https://www.visitfinland.com/en/
Photo: Aurora borealis over the water. Credits: Unsplash/Niilo Isotalo
