five questions about solar storms, which are expected to multiply during the year and could have consequences on Earth

Inhabitants of polar zones (and even those of less extreme latitudes) will see all the colors. The northern and southern lights will increase in number in the coming months, because solar flares, which are the cause of these nocturnal spectacles, will be particularly numerous. Solar storms are linked to the activity of the Sun, which experiences eleven-year cycles and is currently in a phase of high activity. The European Space Agency (ESA) reported, on February 23, the occurrence of the most powerful solar flares of the current cycle.

THE peak is expected towards the end of the year or the beginning of the next, specifies Frédéric Pitout, assistant astronomer at the Institute for Research in Astrophysics and Planetology (Irap). Until then, activity will increase. It could even have concrete consequences on our daily lives. A phenomenon which raises questions to which Franceinfo provides answers.

1 What is the origin of solar flares?

Solar flares are manifestations of “changing magnetism” of the Sun. The latter, summarizes Frédéric Pitout, behaves like a gigantic magnet which, during each cycle, changes direction. This significant modification is accompanied by an increase in its activity, visible in the spots appearing on its surface.

On February 13, the European Space Agency published two images of the Sun taken by its Solar Orbiter probe. The first was taken in February 2021, while the most recent minimum of activity dates back to December 2019. The surface of our star appears relatively homogeneous.

The second was taken in October 2023. At this time, the Sun was not yet as active as in February 2024. However, the panorama is clearly different from the previous image. Here, large and numerous spots are clearly identifiable.

These spots, witnesses to the activity of our Sun, are the foci of solar flares – scientists use the term “coronal mass ejections” (CME). During these events, the Sun expels plasma, “very hot electrically charged gas”, summarizes Frédéric Pitout. We speak of solar storms when the power of these phenomena is high.

2 How big is a solar flare?

The scale of a solar flare is astronomical. Sunspots can be several times the diameter of Earth (which is about 12,750 km). The one that generated the strong eruption of February 22 (called AR3590) was approximately 16 times the diameter of our planet, according to scientific mediator Pierre Henriquet. It was a class X eruption, the most powerful category of five degrees: A, B, C, M and

The filaments that rise from the spots during solar flares can extend tens of thousands of kilometers. NASA, the American space agency, has shared an image to compare the size of Earth and the X-class flare of February 21.

3 What happens when a solar storm hits Earth?

The Sun constantly releases elements, very slow, low energy particles. This is what partly forms the solar wind, in which the environment of our star is bathed. This bubble, called the heliosphere, is very extensive, as this NASA image illustrates.

The particles of solar flares are “very highly accelerated, sometimes to fractions of the speed of light” (around 300,000 km per second), notes specialist Frédéric Pitout. Some can take several days to reach us while the quickest can arrive in around fifteen hours, while the Sun is on average nearly 150 million kilometers away.

Highly energetic, these particles collide with the Earth’s magnetic barrier, called the magnetosphere. They pass through it and end up coming into contact with the earth’s atmosphere. This is where they give rise to the famous Northern Lights (in the Northern Hemisphere) or Southern Lights (in the Southern Hemisphere).

4 What damage could solar flares cause on Earth?

Behind the magical lights of the Northern and Southern Lights lie potential problems for our electrical infrastructure and our satellites, in the event of a particularly violent solar flare, warns franceinfo Olivier Katz, forecaster at the Alps Operational Space Meteorology Center .

“In the event of a strong solar flare, anything that is ferrous, that can conduct electricity and that is very long on Earth, such as pipelines or electrical cables, can be affected by surges. We can imagine blackouts .”

Olivier Katz, space weather forecaster

at franceinfo

An extreme solar storm “could affect critical infrastructure and put a stop to certain economic zones”agrees expert Quentin Verspieren, coordinator of the Protect project within the ESA.

The last documented violent episode dates back to 1859. It is nicknamed the Carrington event, after the British astronomer who studied it. During this eruption, there was so much electricity generated that telegraphs had been damaged and people had been able to communicate via these message transmission systems, while they were disconnected, notes Olivier Katz. He points out that the Northern Lights had also been observed very far from the poles, in the Caribbean.

An event as powerful as Carrington in the 21st century “could put almost all satellites in orbit out of service and severely affect power grids”, writes La Cité de l’espace, reporting the conclusions of a 2013 study for the insurer Lloyd’s. For North America alone, the loss bill could amount to some $2.6 trillion.

A solar storm of incredible violence passed near the Earth in 2012. It could have “return contemporary civilization to the 18th century” if it had reached our planet, according to NASA. An extraordinarily powerful event could damage critical facilities on the ground that would take a generation or two to repair or replace, warns Oliver Katz.

The proliferation of electronic devices and our ever-increasing use of devices relying on satellite data make us more vulnerable than ever to solar storms. “When you use Google Maps to find your route and go to a restaurant, the map was made with Earth observation satellites. For the little blue dot that locates you, and the calculation of the best route, you use navigation satellitesunderlines expert Quentin Verspieren.

This type of research can be done throughout the world thanks to telecommunications satellites, continues the coordinator of the ESA Protect project, noting that we also know whether or not to take our umbrella thanks to satellites of weather report. “Finally, this gesture which may seem trivial uses satellite data which comes from infrastructures which cost hundreds of billions of euros in total”he emphasizes.

Just a disruption in satellite navigation and timing services, which work together, would have cascading consequences. Electricity networks, on a country or continent scale, transport networks or even telecommunications are also coordinated with these satellites and would be affected, he insists.

“The international financial system, and the banking system in general, is regulated with this. The stock exchanges would be blocked and we would not be able to withdraw money from ATMs or pay by card.”

Quentin Verspieren, from the European Space Agency

at franceinfo

If our dependence is great and the potential impacts are significant, the specialists contacted by franceinfo call for us not to fall into catastrophism, emphasizing the rarity of events that could be highly problematic.

5 Are we able to anticipate solar storms?

Our knowledge of the Sun’s magnetism is still far from perfect. For example, its peak activity was expected for 2025, but it could ultimately occur a little earlier, which shows our shortcomings. The process by which sunspots appear, as well as their precise behavior, still remains mysterious. It is also still difficult for us to evaluate the travel time of particles ejected during eruptions. “We still have a lot of uncertainty”concedes Quentin Verspieren.

However, knowledge is progressing, thanks to ongoing missions, such as that of Solar Orbiter, and will be further expanded with the ESA’s Vigil mission, in 2030. The objective is in particular to refine our weather forecasts of space for authorities to issue warnings and take precautionary measures in the event of a severe solar storm. This could involve, for example, grounding planes for the necessary time (several hours or several days) to avoid problems if satellite navigation systems were to be disrupted or interrupted.

Quentin Verspieren adds that discussions have begun, across the European continent, so that an entity with the appropriate skills is operational for the next cycle, in eleven years. Before that, vigilance is required until the upcoming peak of activity.