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A “severe” geomagnetic storm is coming: will the Northern Lights return to Italy?

Credits: NASA/SDO

A geomagnetic storm of category G4 (therefore “severe” according to the official classification) is expected on Earth between today Thursday 10 October and tomorrow Friday 11 October 2024. To provoke one large coronal mass ejection produced by the Sun Wednesday morning generated by X1.8 class flare (X is the highest class). Given the amount of ejected matter and the direction of solar plasma flow, NOAA’s Space Weather Prediction Center predicts the possibility of a geomagnetic storm intense enough to produce Northern Lights also visible at Italian latitudes. If we are lucky (but that’s not a given!) this evening the auroras will return to color our skies after the spectacular auroras of May 2024.

Visible auroras arriving from Italy? The difficulty of forecasting

In this case, the disturbance of the Earth’s magnetic field is measured with a parameter called Kp indexwhich ranges from 0 to 9. In this case the Space Weather Prediction Center predicts a Kp equal to 8. The sightings of November 2023 testified that we can observe auroral phenomena in Italy (red auroras and/or auroral arcs) with a Kp of 7. It is therefore possible to observe auroral arcs or actual auroras at our latitudes.

Be careful, though: having a high Kp is no guarantee of auroras. In fact, to form – and to be visible even at our latitudes – they need not only sufficient geomagnetic disturbance, but also the right alignment between the flow of particles expelled from the Sun and the magnetic field of our planet. Without this alignment, in fact, the particles simply cannot penetrate the “geomagnetic shield”. On the other hand, with a particularly favorable alignment we may or may not have aamplification of the geomagnetic responsepotentially capable of evolving the geomagnetic storm to category G5 (the highest), as happened in May 2024. Everything will depend on the exact polarity of the fields at the moment of arrival of the solar plasma, but this is a quantity that is difficult to predict.

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Red Northern Lights visible in the Belluno area. Credits: Weather in Pills – Emilia and surroundings.

How to look for the Northern Lights

Any auroras or auroral arcs will be visible low on the horizon looking north. Given the randomness of the phenomenon, there is no precise time when we expect to see the lights in the sky. In this case, the absence of the Moon (we are in the new moon phase) and the forecast of clear skies over most of the peninsula would provide good visibility conditions.

The Northern Lights are among the most unpredictable atmospheric phenomena, so be wary of those who assure you that we will see spectacular things tonight: the only way to find out is to raise your eyes to the sky and hope that the May 2024 show will be repeated! In any case, it is possible monitor the trend of the auroral arcs and the geomagnetic disturbance scale on the NOAA website.

What caused the solar storm: a simple explanation

Wednesday 9 October 2024 sunspot AR 3848 produced a great one solar flarethat is, a sudden release of energy (which was previously stored in the magnetic field of the Sun) in the form of electromagnetic radiation. The latter are classified as low in terms of their intensity of energy emitted, with i X-class flares (the more energetic ones). The flare, class X1.8, caused a radio blackout in the half of the Earth exposed to the Sun.

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Thanks to data from the SOHO probe (Solar and Heliospheric Observatory) from NASA, scientists determined that the flare was accompanied by a coronal mass ejection (CME): it means that the energy released by the flare has “pumped” a portion of the solar surface, giving it enough energy to escape in the form of a violent jet of matter. The CME’s trajectory was pointing towards Earth, and currently is moving through space at the speed of 4.3 million km/hone of the highest recorded recently by scientists. At this speed, it is expected to reach our planet between afternoon and evening today.