The (rare) spectacle of the northern lights over Cortina and the Dolomites

2023-11-06 11:28:13

PAOLO VIRTUANI (CURIERE DELLA SERA)

Updated Monday, November 6, 2023 – 10:28

Seen in Italy on Sunday night, it is an unusual phenomenon in those latitudes. It was caused by an intense solar storm that reached Earth

The northern lights seen from the Faloria Refuge over Cortina d’Ampezzo.@Daniele_V94

This is not an unusual event, but it is not a phenomenon that occurs very often in Italy either. On Sunday night, shortly after sunset, the sky over Cortina and the Dolomites was illuminated by an aurora borealis. Numerous videos and photos documenting this rare astronomical phenomenon in the southern Alps have already appeared on social media.

The aurora has been seen throughout Europe: from Poland to Slovenia. This aurora was caused by a solar storm of category G3, (maximum G5)so strong that within the Arctic Circle the aurora was seen even during the day, when there is sunlight, which only happens once every ten years.

In the next few hours, the aurora will also be visible over Norteamrica. The spectacular aurora was also seen in France and in Italiaeven over the Po delta.

Why are they produced?

The polar aurorae (borealis and australia) are produced by the interaction with the Earth’s magnetic field of the flow of charged particles emitted by the Sun in cycles of maximum and minimum activity that last about 11 years. Since late 2019, our star has entered cycle 25 (calculated from 1755) and is ascending towards the cycle high that will be reached in the second half of 2025. The closer the cycle maximum approaches, the more the number of sunspots and associated flares increases.

Colors

The spectacle of the polar auroras is due not only to their incessant movement across the sky, but also to their colors. The color verde It is produced by the interaction of solar particles with atomic oxygen in the upper atmosphere at an altitude of about 100-160 kilometers, the color blue violet by nitrogen atoms about 90-100 kilometers above the surface. The color rojo It only manifests itself in very intense solar storms that also excite molecular oxygen (O2) at altitudes of about 240 kilometers, giving the night sky its typical blood red color.

Galileo

The northern lights were known in ancient times, Chinese and Greek chronicles speak of them, and on rare occasions they have been observed in Italy. The term “aurora borealis” was coined by Galileo Galileibut the physical phenomenon was only fully explained at the beginning of the 20th century by the Norwegian scientist Christian Birkeland through the propagation of electrical currents in space caused by solar storms that interact with the atoms of the Earth’s atmosphere. But he was not believed and it was not until the 1960s, with the first satellites, that Birkeland’s theory was proven correct. Birkeland was nominated for the Nobel Prize seven times, but he never won it. He won it in 1970 the Swede Hannes Alfvnwhich took up and improved Birkeland’s theories in light of new satellite data.