This Wednesday, January 1, the Northern Lights lit up the sky in our territory and were also observed in Limousin. What is their origin? Why are they visible here? How to explain their color? Can we predict their appearance? The Limousin Astronomy Club agreed to answer our questions.
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No need to fly to Iceland or Norway… Limousin is enough. To start the year 2025, the Northern Lights lit up the night from Wednesday January 1 to Thursday January 2. From Haute-Vienne to Creuse, via Corrèze, several Internet users have immortalized this moment and shared their photographs on social networks. The phenomenon has also been observed in other French territories, such as Corsica or Jura. What is its origin? Why does it appear in our latitudes, and not only at the North Pole? How to explain green or red colors? Can we predict it? Christian Pantacchini, president of the Limousin Astronomy Club based in Beyssac, answers our questions.
The sky over Salon-la-Tour, in Corrèze, on the night of Wednesday January 1 to Thursday January 2, 2025.
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© Fabien Maury
What is the origin of the Northern Lights?
“The Northern Lights come from particles emitted by the Sunexplains Christian Pantacchini. It is a star in perpetual activity which ejects hot bodies in all directions. This is commonly called solar winds.“The encounter between these solar winds and our planet is precisely what the general public observes and ends up calling “aurora borealis”.”What people see in the sky is the fruit of this encountercontinues the enthusiast. Particles that enter our atmosphere will collide with the gas molecules that surround our planet. They will excite these molecules, which will produce light.“It is this generated light which will form the immense variegated sails which seem to float in the sky.
Why are they observable in Limousin?
Most often, the Northern Lights are a phenomenon reserved for the poles of the globe, particularly the northern territories. The Earth's magnetic field acts as a kind of shield that rejects solar winds towards the Arctic and Antarctic circles. “This is when solar activity is normalsays Christian Pantacchini. But here we are experiencing a very intense phase. The Sun emits a lot of particles. When there are more of them and they are powerful, they are not all moved north or south. They remain in our latitudes and we can contemplate them.“
But then, why is our star starting to eject more particles than usual? “It's a question of cycle. Basically, we generally consider that the Sun experiences peaks approximately every eleven years. Without being too technical, we can say that it alternates between phases of weak magnetic activity and phases of high magnetic activity there, we are going through a period of solar maximum which will continue in 2025 and probably reduce thereafter.
How to explain their different colors?
Usually, the photos captured by nature photographers show us green-tinted Northern Lights. However, this Thursday, January 2, the images shared by French Internet users show a rather orange, even reddish, sky. “It's a question of altitudespecifies the president of the Limousin Astronomy Club. When it is green, it means that the particles coming from the sun have encountered nitrogen molecules, between one hundred and two hundred kilometers in altitude. When the collision occurs higher up, they only encounter oxygen: this gives red, like in our case.“
How to predict their appearance?
Although the Northern Lights are difficult to predict, certain atmospheric conditions can be favorable. “There is the KP index, which allows us to estimate the importance of solar winds and their speedexpose Christian Pantacchini. It's a scale that goes from 0 to 9. For the phenomenon to be observable here, it really has to be at the highest level. Then, the other essential parameter to monitor is the Earth's magnetic field. It must direct the solar particles in the « good direction ». This is notably determined by the BZ index. These data are available on the “Space Weather Live” website. It tells us the chances we have of seeing the Northern Lights, and in which areas of the globe. Anyone can view it!“
Another possibility: the “My Aurora Forecast” smartphone application. Very popular and easy to access, intended for laymen and experts alike, it lists the best places for observing the lights of the sky. Enough to occupy the evenings of Limousins in the coming months.
