The Sun is on the brink of a major event: a magnetic field reversal.
This phenomenon occurs roughly every 11 years and represents an important phase in solar cycle. A polarity shift indicates the halfway point solar maximumthe height of solar activity and the beginning of the shift to solar minimum.
Last sunThe reversal of the magnetic field occurred at the end of 2013. But what causes this polarity reversal and is it dangerous? Let’s take a deeper look at the reversal of the Sun’s magnetic field and explore the effects it could have on it Earth.
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To understand magnetic field reversals, it is first important to know the solar cycle. This approximately 11-year cycle of solar activity is controlled by the Sun’s magnetic field and is indicated by the frequency and intensity of solar radiation. sun spots visible on the surface. The height of solar activity during a given solar cycle is known as the solar maximum, and current estimates predict that it will occur between late 2024 and early 2026.
However, there is another very important, though lesser known, cycle that includes two 11-year solar cycles. This magnetic cycle, known as the Hale cycle, lasts approximately 22 years, during which the Sun’s magnetic field reverses and then returns to its original state. Ryan Frenchsolar astrophysicist and contributing writer for Space.com, told Space.com.
During solar minimum, the Sun’s magnetic field is near a dipole with one north pole and one south pole, similar to 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,” French said. By the time solar maximum passes and solar minimum arrives, the Sun has returned to the dipole, albeit with reversed polarity.
The upcoming polarity change will be from a north to south magnetic field in the northern hemisphere and vice versa in the southern hemisphere. “This puts it in a similar magnetic orientation to Earth, which also has its southern magnetic field in the northern hemisphere,” French explained.
What causes polarity reversal?
The reversal is driven by sunspots, magnetically complex regions of the Sun’s surface that can cause significant solar events such as solar flare and coronal mass ejections (CMEs) — large bursts of plasma and magnetic field.
As sunspots appear near the equator, they will have an orientation consistent with the old magnetic field, while sunspots forming closer to the poles will have a magnetic field consistent with the incoming magnetic field, French said. This is called Hale’s Law.
“The magnetic field from the active regions makes its way toward the poles and eventually causes a reversal,” said solar physicist Todd Hoeksema, director of the Wilcox Solar Observatory at Stanford University. he previously told Space.com.
But the exact underlying cause of such polarity reversal remains mysterious. “It fits into the whole [solar] cycle and I wonder what it is,” solar physicist Phil Scherrer of Stanford University previously told Space.com. “We still don’t have a really consistent mathematical description of what’s going on. And until you can model it, you don’t really understand it—it’s hard to really understand it.”
It really depends on where the magnetic field comes from. “Will there be many sunspots? And will the sunspots contribute to the pole’s magnetic field, or will they somehow cancel out locally?” said Hoeksema. “We don’t know how to answer that question yet.”
How quickly does the switch happen?
What we do know is that the reversal of the solar magnetic field is not instantaneous. It is a gradual transition from a dipole to a complex magnetic field, to a reversed dipole over the entire 11-year solar cycle. “In short, there is no specific ‘moment’ at which the sun’s poles flip,” French said. “It’s not like on Earth, where overturning is measured by north/south pole migration.”
Full reversal usually takes a year or two, but can vary greatly. For example, the north polar field of solar cycle 24, which ended in December 2019, took nearly five years to reverse, according to National Solar Observatory.
The reversal of the magnetic field is so gradual that you don’t even notice when it happens. And no, as dramatic as it may sound, it’s not a sign of the impending apocalypse. “The world won’t end tomorrow,” Scherrer said earlier Space.com.
However, we will experience some side effects of the polarity reversal.
How does the sun’s magnetic reversal affect us?
There is no doubt that the Sun has been incredibly active recently, firing off many powerful solar flares and CMEs, triggering powerful geomagnetic storms on Earth, which in turn have caused incredible northern lights lately.
However, increased severity space weather is not a direct cause of polarity reversal. Rather, these things occur together, Hoeksema told Space.com in 2013.
According to French, space weather is usually strongest during solar maximum, when the Sun’s magnetic field is also at its most complex.
One side effect of the shift in the magnetic field is small but mostly beneficial: it can help shield Earth from galactic radiation cosmic rays — high-energy subatomic particles that travel at speeds close to the speed of light and can damage spacecraft and harm orbiting astronauts outside Earth’s protective atmosphere.
As the Sun’s magnetic field shifts, the “current sheet”—a vast surface that radiates billions of miles outward from the Sun’s equator— becomes very wavyproviding a better barrier against cosmic rays.
Predicting the future forces of the solar cycle
Scientists will closely monitor the reversal of the Sun’s magnetic field and see how long it takes for it to bounce back to a dipole configuration. If this happens over the next few years, the next 11-year cycle will be relatively active, but if the build-up is slow, the cycle will be relatively weak, like the previous Solar Cycle 24.