The Sun’s magnetic field will reverse, and that’s good news for Earth

The activity of the Sun does indeed have repercussions on Earth. In recent weeks, it has been possible to observe the Northern Lights in France. But in the United States, it was farmers who were hit with a severe disruption to their GPS instruments, preventing some from continuing their sowing.

These phenomena were the consequence of a peak in solar activity, which follows a cycle of approximately 11 years. These repercussions take place as the Sun begins the end of this cycle, which brings it into its solar maximum, its period of strongest activity. It is expected between the end of the year and the beginning of 2026, specifies Space.com.

But this time, the Sun’s activity cycle is accompanied by another lesser-known phenomenon: the Hale cycle. This is a magnetic cycle that spans approximately 22 years and sees the Sun’s magnetic poles reverse and return to their initial state.

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Sunspots proliferate just before the Sun’s polarity reverses

Each time the Sun’s activity increases, its magnetic field becomes more and more complex. Instead of displaying a dipole, as is the case most of the time, the north and south poles are no longer clearly distinguishable. When this peak of activity has passed, the dipole configuration of the Sun is again visible, but their polarity has been reversed.

This change is a consequence of the proliferation of sunspots. They appear massively during the star’s peak activity and present intense magnetic fields on the surface of the Sun. It is in particular because of their presence that solar flares occur, generating magnetic storms, or even coronal mass ejections (plasma bubbles which form on the surface of a star).

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“The magnetic field of active regions moves towards the poles and eventually causes the reversal”details Todd Hoeksema, director of the Wilcox Solar Observatory at Stanford University, to Space.com.

However, if the phenomena and consequences are well identified, the reason behind the reversal of the Sun’s polarity remains a mystery. “We still don’t have a coherent mathematical description of what’s happening.”describes Phil Scherrer, a solar physicist at Stanford University. “And until you can model it, you don’t really understand it.”he continues.

How Earth benefits from the reversal of the Sun’s magnetic field

Thus, it is today impossible to know what is really happening on the surface of the Sun. In the northern hemisphere of the star, the northern magnetic field is about to become the southern magnetic field, and vice versa in the southern hemisphere. This will make the Sun correspond with the Earth’s magnetic field.

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The peak of solar activity and the reversal of its magnetic poles will therefore be particularly scrutinized by the scientific community. This will notably involve knowing how sunspots contribute to the magnetic field of each pole, or whether the reversal of polarity cancels them out locally. “We don’t yet know how to answer these questions.”admits Todd Hoeksema.

What is certain is that the polarity reversal of the Sun will have an impact on the Earth. A positive impact. As it moves, the star’s magnetic field ripples the “current sheet”, a surface of billions of kilometers extending from the Sun’s equator.

These undulations form a sort of barrier against cosmic rays. Cosmic rays are made of high-energy subatomic particles that travel at close to the speed of light. The only problem is that they can damage spacecraft or injure astronauts located outside of Earth’s protective atmosphere. A danger which will therefore, for a time, be reduced by the reversal of the polarity of the Sun.