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Northern lights near Schilling in the district of Friesland

Photo: Markus Hibbeler / dpa

A colorful night sky, in Germany such a sky is rarely seen. On Monday night, however, onlookers were lucky: Northern lights could be seen in several federal states. In parts of Saxony-Anhalt, Brandenburg, Schleswig-Holstein and Lower Saxony, the celestial spectacle showed, reported several dpa reporters, among others. The night sky shone in different colors such as green, purple, yellow and red. Especially in rural areas, the lights could be seen well.

According to the German Research Centre for Geosciences (GFZ), auroras occur mostly in the far north between 60 and 70 degrees latitude. For orientation: Oslo is located just below the 60th parallel, the Norwegian city of Tromsø just below the 70th parallel. However, during strong solar storms, the Northern Lights can be seen further south.

Basically, the stronger the solar storms, the better the visibility for the more southern latitudes, explained a spokesman for the GFZ. One measure of the strength of a solar storm is the Kp index. A Kp index between 0 and 3 indicates low solar activity, and with a Kp value of 9, auroras would even be above central Germany – for example Dresden or Kassel. In very rare cases, they can also be seen from the Alpine region. The prerequisite for this is clear skies and a clear view to the north.

Just a few days ago, auroras had been spotted over Saxony-Anhalt. At that time, the Kp index reached a rather high value of 6.333. On Monday night, the value was a maximum of 5.667. The value of 22 has already been exceeded 6 times this year. Values beyond 8 were only reached three times, according to the GFZ spokesman. The 9 did not yet exist on the Kp index this year.

Relatively high values of the Kp index are currently not unusual, according to the spokesman. As solar activity increases, such geomagnetic storms are also becoming more frequent. The play of light in the sky is triggered by so-called high-energy solar wind particles, which are thrown into space at high speeds by eruptions on the sun's surface and hit the Earth's magnetic field.

Back in April, a spokesman for the Institute of Solar Terrestrial Physics at the German Aerospace Center (DLR) announced that the current increase in sightings is not entirely unusual. About every eleven years, in a so-called solar cycle, there are phases with weak and strong solar activity. Currently, a maximum is approaching, which is expected in 2025. Statistically, spring and autumn are the best seasons to spot the Northern Lights in Germany.