© Vincent Guth/Unsplash
For several nights, a spectacle of rare beauty has been unfolding in the sky: aurora borealis of unusual intensity, in vibrant shades of green and red, illuminate the sky well beyond their usual latitudes. France itself was affected during the Ascension weekend, as well as other areas of the world: Austria, Switzerland, California and even Russia.
This extraordinary phenomenon, directly linked to solar storms of remarkable magnitude, recalls the great disturbances of 2003, known as the “Great Halloween Solar Storms”. “. A series of powerful solar storms that occurred from late October to early November 2003. These were among the most powerful on record and caused very significant disruption on Earth. While these celestial events are not without risk, they have so far fascinated people more by their beauty than by their destructive potential. The last few days have been no exception.
The origin of the storms: massive solar disturbances
If these auroras were so spectacular, it’ ;is that they were caused by two major geomagnetic storms of level G5, considered among the most intense possible on the scale used for measure this type of phenomenon. The latter, of phenomenal power, were triggered by coronal mass ejections (CME), gigantic explosions of plasma and magnetic fields expelled by the Sun.
These CMEs come from a region of particularly intense solar activity, identified as AR 3664. This area, known for its propensity to generate class X solar flares, the most energetic and powerful there is, recently released a series of solar events of exceptional magnitude.
It is precisely this interaction between CMEs and the Earth's magnetic field which is at the origin of the magnificent northern lights that we have been able to observe in recent days. At least the lucky few who were able to attend When energetic particles projected by the sun hit our planet, they are guided by the Earth's magnetic field towards the poles. At that point, they collide with molecules in the atmosphere,thus creating these fascinating glows undulating in the sky.
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Visible and invisible consequences
The color of the aurora depends on several factors  ;: the altitude at which interactions between solar particles and the Earth's atmosphere occur. These interactions occur mainly in the thermosphere, at altitudes between 80 and 300 km above the Earth's surface. The nature of the solar particles involved in the process also play a role in the coloring of the auroras (protons or electrons). Green auroras are the most common and generally result from interactions at altitudes between 100 and 300 km. They are mainly due to the excitation of oxygen atoms. On the other hand, red auroras, of a more flamboyant hue, come from higher reactions, between 300 and 400 km, and involve nitrogen molecules. These manifestations are the tip of the iceberg.
The invisible part of the Sun's activity on Earth can have quite significant consequences. These solar storms can, in fact, cause serious disruptions to electrical networks, potentially affecting the operation of certain devices and infrastructure. Likewise, satellite and radio frequency communications may be temporarily disrupted. These impacts often go unnoticed by the general public, but this is not always the case.
Certain solar flares in the past have had effects which, for once, have been perfectly visible. In March 1989, a geomagnetic storm of rare violence struck the Earth. Caused by an eruption 36 times the size of the Earth, it caused real panic. More than six million Quebecers found themselves without electricity for nine hours and a UN military operation in Namibia was also disrupted. Occurring in the middle of the Cold War, some even believed in a surprise nuclear attack.
Currently, solar storms are quite intense and solar activity, approaching the peak of its 11-year cycle, < strong>it is very likely that other demonstrations of the same scale will occur again. Researchers and forecasters, particularly those from NOAA (National Oceanic and Atmospheric Administration), have their eyes glued to the sky to monitor these phenomena to assess the risks. In the meantime, the aurora spectacle will continue to make our eyes shine!
- In recent days, many northern lights have dotted the sky in unusual places.
- A phenomenon caused by two violent geomagnetic storms that occurred in the AR 3664 region of the Sun.
- These storms can also seriously disrupt power grids.
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