It’s official: NASA has just confirmed that we are now at the heart of the solar maximum, the peak of the activity cycle of our star. Its magnetic field is now on the verge of reversing, and we must therefore expect solar weather to pick up over the next few months – without panicking too much, but remaining aware of what the Sun is capable of.
From Earth’s perspective, the Sun looks like an imperturbable guardian angel, shining steadily since our planet’s genesis. But over the centuries, astronomers have realized that it is not as immutable as our ancestors thought. It actually follows a relatively precise cycle, even if it is difficult to predict its exact limits.
The peak of an eleven-year cycle
We know that this cycle lasts eleven years on average, and that it is delimited by abrupt reversals of its solar magnetic field. This is an observation that has now been well established for almost several centuries. Yet researchers still struggle to understand all the nuances of the solar dynamo, the mechanism behind this magnetic field. In fact, it is one of the most enduring mysteries in all of astrophysics; we still do not know exactly what generates this magnetism, nor why the resulting field regularly switches.
On the other hand, if the underlying phenomena remain quite enigmatic, we know that this cycle is closely linked to the number of sunspots. This term refers to the famous dark areas that you have undoubtedly already seen in many photos of the Sun; they appear where particularly intense magnetic field lines emerge from the surface and disrupt the flow of plasma surrounding the star.
When the inversion approaches as it is now, we enter what is called the solar maximum. This corresponds to a drastic increase in the number of sunspots, but also and above all in all the phenomena associated with them.
Indeed, during this period, these field lines become particularly unstable and dynamic; they are much more likely to break and reconnect violently. If necessary, this produces a powerful discharge of X and gamma rays, ultraviolet and radio waves which strongly disrupts the atmosphere of the Sun and other neighboring objects: we speak ofsolar flare.
Sometimes, these eruptions can also tear off an immense bubble of plasma, made up of several billion tons of charged particles. This cloud thus finds itself catapulted in a very specific direction at a dizzying speed, sometimes of the order of 3000 kilometers per second. We call this a coronal mass ejection, or CME pour Coronal Mass Ejection.
Solar weather, a threat to our civilization
These two phenomena can have very concrete consequences for our planet. When these streams of charged particles approach, they transfer some of their energy to Earth’s magnetosphere, causing what is called a geomagnetic storm. These often appear in the form of auroras – but the most violent ones can also disrupt communication and navigation systems.
Beyond a certain threshold, these storms can even generate a significant current in conductive materials. This can impact the functioning of our electronic devices. This is particularly true for rockets and satellites, which operate in an area where the Earth’s magnetic field is slightly weaker. For example, last July we learned that a powerful solar flare had caused unprecedented discord in orbit.
In the most extreme cases, the situation can even become downright catastrophic. The most famous example is the Carrington Event, a powerful geomagnetic storm that struck Earth in 1859. By some estimates, the CME that caused this event released as much energy as 10 billion atomic bombs, and slammed into the Earth’s magnetic field like a veritable cosmic battering ram.
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This caused numerous spontaneous fires throughout the telegraph network, and operators even suffered electric shocks without the reason being immediately apparent. However, at the time, humanity was much less dependent on electrical infrastructure.
If a phenomenon of this kind occurred today, it could result in a chaos never before seen in our modern society. This is particularly why astronomers monitor our star like milk on fire during solar maximum, where flares (and by extension, CMEs) become significantly more frequent and intense.
A lesson in humility from space
The good news is that Carrington-type episodes remain relatively unlikely. Certainly, these ultra-violent eruptions are not statistical anomalies that occur every few million years; on the scale of a human life, this is a very concrete possibility. Fortunately, the chances of such a CME hurtling toward Earth are relatively low. The last CME of this magnitude, in 2012, passed relatively far from our planet without harmful consequences. There is therefore no reason to give in to catastrophism.
But even if the statistics work in our favor, we can also see this solar maximum as a new booster shot. This remains a good opportunity to remember that it is appropriate to remain humble in the face of the whims of our staragainst which we remain relatively powerless at present. Let us therefore hope that it will be lenient over the coming months, and that we will be able to approach the next solar cycle calmly after the imminent reversal of its magnetic field!
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