The Sun is preparing to reverse its magnetic field. What does this mean for Earth and humanity?

The Sun is on the verge of a major event: a reversal of its magnetic field. This phenomenon occurs approximately every 11 years and represents an important phase in the solar cycle. The polar shift marks the midpoint of solar maximum, the height of solar activity, and the beginning of the shift toward solar minimum.

The last time the sun’s magnetic field flipped was at the end of 2013. But what causes this polar shift and is it dangerous? Let’s take a deep dive into the reversal of the Sun’s magnetic field and explore the effects it can have on Earth.

To understand magnetic field reversal, first, it is important to become familiar with the solar cycle. The roughly 11-year cycle of solar activity is driven by the Sun’s magnetic field, indicated by the frequency and intensity of sunspots visible on the surface. The peak of solar activity during a given solar cycle is known as a solar maximum, and current estimates predict that it will occur from late 2024 to early 2026.

“But there is another very important cycle, although it is less well-known, and it includes two solar cycles, each lasting 11 years. Solar astrophysicist Ryan Frenz says that this magnetic cycle, known as the Hale cycle, lasts about 22 years, during which the Sun’s magnetic field reverses and then Returns to its original state.

During solar minimum, the Sun’s magnetic field is close to a dipole, with a north and south pole, similar to the Earth’s magnetic field. But as we move toward solar maximum, “the Sun’s magnetic field becomes more complex, with no clear north-south separation,” says Frijns. By the time it passes solar maximum and reaches solar minimum, the Sun has returned to its dipole, albeit with a polarity reversal.

The next change in polarity will be from the magnetic field from north to south in the Northern Hemisphere and vice versa in the Southern Hemisphere. “This would put it in a magnetic orientation similar to Earth, which also has a southerly magnetic field in the Northern Hemisphere,” explains Frinz.

Explosions

The reflection is caused by sunspots, which are magnetically complex areas on the Sun’s surface that can cause large solar events such as solar flares and coronal mass ejections (CMEs), which are large explosions of plasma and magnetic fields. These explosions occur at points on the Sun that at that moment see the Earth sending to our planet a tsunami of charged particles that cause natural phenomena such as the aurora borealis but at the same time cause operational problems in communications satellites and electrical networks.

During solar maximum, a large number of sunspots are visible at mid-latitudes, and during solar minimum, a very small (sometimes zero) number of sunspots are visible at the equator. “With sunspots forming near the equator, they will have a direction that matches the ancient magnetic field, while sunspots that form near the poles will have a magnetic field that matches the incoming magnetic direction. This is called Hill’s Law,” says Frenz.

“The magnetic field from the active regions moves toward the poles and eventually leads to a reversal,” says solar physicist Todd Hoeksema, director of the Wilcox Solar Observatory at Stanford University.

But the reason behind this polar reversal remains a mystery. “This goes into the entire solar cycle and I wonder what it is. We still don’t have a really consistent mathematical description of what’s going on. Until we can model it, it’s hard to really understand it,” says Phil Scherer, a solar physicist at Stanford University.

It really depends on the source of the magnetic field. “Will there be a lot of sunspots? Will sunspots contribute to the polar magnetic field or will they cancel out locally? We don’t know yet how to answer this question,” says Hoeksema.

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