Aurora Borealis/SAR over the skies of Northern Italy today 19 April 2024

New sighting of the Northern Lights/SAR over the skies of Northern Italy, especially the Alps: some webcams and the quick reflexes of numerous spotters immortalized the show

After the sensational show of the Northern Lights on 5 November 2023 (preceded by another warning between 24 and 25 September) the Northern Lights (although it was most likely a SAR) were spotted over the skies of Northern Italy, mainly the Apennines Modena and the Alpine arc of the middle Triveneto. We probably could have had many more reports in the North-East Alps, but the weather is terrible and in the areas where, it is estimated, there could have been the best sightings in the national territory, it is cloudy or it is raining/snowing in the mountains.

The beautiful shot by Tita Lorenza Fain from Tambre, province of Belluno

As anticipated in the previous paragraph, perhaps it was not a simple Northern Lights, but rather a much more complex phenomenon (the one that generated the greatest spectacle over Italy last November, with SAR sightings as far away as the Gargano!). Let’s look at the differences together:

SAR stands for stable red auroral archin English “stable auroral red arc”. Typically red in colour, it is often considered an “appetizer” of the actual aurora, and for this reason, during significant geomagnetic storms, it is not difficult to come across this phenomenon. They are the result of dynamics triggered within the Van Allen belt, with enormous shifts of thermal energy in the Thermosphere which transport millions of amperes around our planet, generating large red “doughnuts” which can travel great distances in just a few minutes. , and for this reason the SAR, when visible, lasts about 5 minutes, so you have to be very quick in your observation and photos! In a normal situation, the SAR bands, thanks to terrestrial magnetism, trap solar particles at important heights, but in the case of geomagnetic storms, the terrestrial magnetic field can be slightly weakened, lowering the height of the SAR and making the phenomenon visible lower. However, very significant storms are needed to allow naked eye observation, as the SAR light spectrum is generally very weak.

L’NORTHERN LIGHTS it is an atmospheric optical phenomenon, just like lightning and rainbows. Unlike SARs, the aurora borealis are generated by electrons (solar wind) which are pushed towards the Earth’s magnetic field, colliding at very high speed with gases and particles in the external areas of our atmosphere. Due to the shape of our Planet, the poles are more exposed and receive the charge of electrons in larger doses from the Sun. The movement of these particles produces energy and therefore light (all at a height of about 70-120 km on the sea level) of different wavelength and color. Green is the most frequent color and auroras can have this color even in the case of solar activity and mild solar flares, while red is the rarest color and indicates powerful solar flares (and this is also why it is easy to confuse them with SARs) . The aurora is also distinguished from the SAR due to its shape: the auroras are sinuous and dance in the sky even for hours, in the most fortunate cases, and appear in elongated shapes or in the form of moving pillars. SARs are actual arches which, when visible, flow rapidly from North to South without creating particular shapes.