If you like beautiful, exceptional natural phenomena, astronomy, interactions between terrestrial and solar magnetism, stellar physics, and live in Strasbourg, Alsace, in the Vosges – or elsewhere around these latitudes: look up the North after 11 p.m. Saturday May 11 or Sunday May 12! Nights of northern lights are very possible. The phenomenon was very clearly visible throughout mainland France, particularly from the Vosges, on the evening of Friday May 10 and even in the cities.
The exceptionally intense geomagnetic storm that caused these auroras is still ongoing, following a large solar flare two days ago. A current large sunspot is linked to intense solar flare activity, and the northern lights these days are visible much further south than usual, as evidenced by the activity and forecasts on this dedicated site or on the International Geomagnetic Activity Indices Service, whose data is produced by the national observation service of the School’s Magnetism Observatory and Earth Sciences Observatory in Strasbourg.
From Strasbourg, or the Vosges, look up towards the Great Bear constellation, that is to say look towards the North. If you are in a city or village, turning off or dimming the street lights at the end of the evening will help you (like those in Strasbourg and various localities which try to preserve the night and the night sky). A phone or camera is more sensitive than your eye (choose a pause time of three seconds for example), but it will be visible enough to be seen with the naked eye, as was the case on the night of Friday the 10th to Saturday May 11 after midnight.
Why is the sky pink?
The colors of these auroras are due to atoms in the atmosphere which are excited by charged particles (mainly protons – hydrogen nuclei, electrons and alpha particles, i.e. two protons, two neutrons, hydrogen nuclei). helium), from a solar flare a few dozen hours earlier. This coronal mass ejection is a plasma bubble emitted during the eruption, of the same composition as the solar wind.
Red auroras are the rarest. They are emitted by oxygen, which is less dense above 240 km altitude. Green, more common, is also emitted by oxygen in denser, lower atmospheric layers, at 120 km to 180 km altitude. We could see them on the evening of Friday May 10, lower on the horizon. Nitrogen emissions are often dark red, purple or white.
The Northern Lights, common in Scandinavia, are often green and pink. Those (very rare) in our latitudes are more commonly red. Charged particles follow the magnetic field by spiraling, usually concentrating around the poles, and slowing down as they interact with the upper atmosphere, hence the auroras. This magnetic shield due to the Earth’s internal dynamo is what protects terrestrial life from too intense radiation – and what astronauts must protect themselves from when exiting the magnetosphere to go further.
