The reports came in en masse between 6pm and 7pm November 5, 2023: the skies of Northern Italy have become tinged with rosso for the phenomenon ofnorthern Lights. The aurora was also visible for several minutes to the naked eye in various regions of Northern Italy but also of Central Italy: Piedmont, Lombardy, Veneto, Emilia Romagna e Marche.
At lower latitudes the aurora could not be seen with the naked eye, but cameras were able to immortalize it through long exposures also in the Southern regions, including the Puglia. These testimonies also confirmed the Red of the dawn.
Observing the Northern Lights at the latitudes of Northern Italy is very rare, but this one is the second time this has happened in less than two months: l’last sightingin Lombardy and Alto Adige, dates back only to the night between 25 and 26 September 2023. In fact, many are wondering if these new images are fakelike other times it happened in the past. Well, this time it is all truebut it is very unusual! So what is happening?
It all started with acoronal mass ejection (i.e. a stream of charged particles emitted from the outer atmosphere of the Sole) emitted a couple of days earlier by our star. Coronal mass ejections are frequent events, but when they hit the Earth they can produce disturbances in the Earth’s magnetic field called geomagnetic storms o solar storms. The storm associated with this expulsion caused auroras visible from all over Europe, including Northern Italy.
Geomagnetic disturbance is measured with an index called Kpwhich ranges from 0 to 9. To see the auroras we must have Kp between 8 and 9; the aurora visible from Italy instead had a Kp of approximately 7. So how come we saw her, and why was she red?
Typically auroras are green, but it is practically impossible to observe green auroras at Italian latitudes. These are formed when charged particles emitted by the Sun interact with oxygen molecules present in our atmosphere a 100-300 km of altitude. If the geomagnetic storm is intense enough, however, it can also interact with individual oxygen atoms present higher up (above 400 km). This interaction produces red auroras, and being higher up it is also visible from a greater distance, even from thousands of kilometers. That’s exactly what we saw here in Italy!
But why two Northern Lights in less than two months, if they are so rare? It’s difficult to give a precise answer. We are certainly helped by the fact that the Sun is approaching its phase maximum magnetic activity compared to its eleven-year cycle, so it is particularly active at the level of flares and, precisely, coronal mass ejections like those that caused the aurora that adorned the European and Italian skies on the evening of November 5th.
The post first appeared on www.geopop.it