That’s right! This extraordinary phenomenon took place during our 5-day weekend and didn’t interest many people! Beautiful, colourful images and a French night sky covered in a drape of pink or green hues, several evenings and nights in a row. Such observations are not common in France. Before looking back at this exceptional episode, which took place between Friday 10 and Monday 13 May, let’s start by recalling how the aurora borealis, or more generally the polar lights, are formed. Known as the ‘aurora borealis’ in the northern hemisphere and the ‘aurora australis’ in the southern hemisphere, they are closely linked to the activity of the Sun.
This luminous phenomenon is formed when the solar wind, a stream of electrically charged particles (protons and electrons) ejected by the Sun, comes into contact with the Earth’s upper atmosphere. It is generally observed in a so-called ‘auroral’ zone, located between 60 and 75 degrees latitude. In other words, in a wide band including Scandinavia, Iceland, northern Canada and Greenland, where the Earth’s magnetic field is too weak to act as a shield against these solar winds.
Within this zone, particles ejected by the Sun penetrate the upper atmosphere more easily. They collide with the gases that make up our atmosphere (oxygen, hydrogen and nitrogen) and excite their atoms. As the atoms change state, they release energy in the form of light.
Billions of collisions occur between solar particles and the gases in the upper atmosphere, all of which emit light. Several billion flashes of light are released, forming an aurora borealis in the sky. A majestic veil of light that can turn from green to red, blue or violet, depending on which atoms are stimulated. That’s why our French skies, so unaccustomed to this kind of display, surprised everyone and disappointed those who didn’t manage to see them (myself included…)
