This morning August 12, 2024 The Earth was hit by a geomagnetic storm of Category G3therefore “strong” according to the official classification. For today, the NOAA Space Weather Prediction Center had issued a warning for a category G2 (“moderate”) geomagnetic storm, due to the arrival of a coronal mass ejection from the Sun associated with a solar flare of class X (the most energetic). However, the SWPC had predicted the possibility that two more ejections of solar plasma could reach our planet by the end of the day, increasing the intensity of the disturbance in the Earth’s magnetic field. And so it was: at 7:25 Italian time the G2 storm caused by the first coronal ejection she moved up to the G3 category following the arrival of the other two emissions. The three ejections did not merge, so it is not a so-called “cannibal storm”.
The geomagnetic storm remained at category G3 for several hours, and at the time of writing it appears to have “returned” to category G2. A category G3 storm can give some problem with the electrical networkscreate temporary losses of satellite orientation and make it difficult radio communication low frequency and intermittent high frequency. Strong geomagnetic storms can also produce Northern Lights visible up to latitudes of about 50°. In fact, the Northern Lights have been spotted in various countries including Germany and the United States, thus adding to the spectacle of the Perseids, the “shooting stars” of San Lorenzo which are at their peak right now.
Speaking of auroral phenomena, last night some webcams in the Alps spotted at around 2:00 am some very distant Northern Lights or more likely the stable auroral arcs (SAR, Stable Auroral Red Arc), the phenomenon that was seen in the Italian skies on November 5, 2023. The sightings occurred in particular in the Cinque Torri area near Cortina d’Ampezzo in the province of Belluno, in Val Senales in the province of Bolzano and in Prato Nevoso in the province of Cuneo.
The SARs are not exactly aurora borealis but they are visibly very similar to the red aurora borealis, the ones we can typically observe here in Italy. Both phenomena form at high altitudes (300-400 km) and have a reddish color due to the excitation of the atoms of oxygen in the upper atmosphere: the main difference is that in the case of auroras the oxygen receives energy directly from the charged particles coming from the Sun, while in the case of SARs the energy transfer mechanism is indirect and involves the Van Allen belts (See our dedicated article for a detailed explanation.) Unlike the Northern Lights, SARs are best seen at intermediate latitudes like ours, due to the arrangement of the Van Allen belts around the Earth.
