The sun’s magnetic poles are about to disappear as they swap polarities, which may lead to a number of geomagnetic storms hitting Earth in their wake.
The sun’s magnetic poles swap positions every 11 years or so as the sun approaches its most active period (solar maximum), with the sun having no magnetic poles and a messy, chaotic magnetic field during the interim. The amount of time that the sun is left with no poles varies from solar cycle to solar cycle.
This swapping of the poles is expected to send increasingly weird space weather our way, in part because of a section of the sun’s magnetosphere called the heliospheric current sheet—a ring of electricity blown out from the sun by the solar wind—becoming wavier than usual.
“The solar polar reversal is a normal phenomenon that occurs every 11 years. We call this the solar cycle,” Daniel Billett, a space physics researcher at the University of Saskatchewan, told Newsweek. “The reversal happens when the poles themselves are about to disappear, but it’s actually when the sun is most active. If you could see the sun’s magnetic field right now, it would be a large tangled web of magnetic field lines without a coherent shape. In half a cycle’s time [5.5 years from now], the poles will be well defined and look more like a bar magnet.”
“What this means is right now, as we are solar maximum with a huge mess of a solar magnetic fields, is we get more solar flares and coronal mass ejections. These can hit Earth and cause geomagnetic storms in our atmosphere, which last year caused the loss of about 50 Starlink satellites.”
Geomagnetic storms are a result of solar flares or coronal mass ejections (CMEs) of solar plasma being flung out from the sun, which usually occurs at sunspots or other areas of high magnetic energy.
“The sun’s magnetic field behaves a little bit like lots of elastic bands which, during the rising phase of the solar cycle which we are now in, become increasingly tangled up and taught,” Gareth Dorrian, a research fellow in space science at the University of Birmingham, told Newsweek. “At some point, all that stored potential energy has to be released, which is the chaotic period called solar maximum.
“Once this stored energy is released, the field returns to a less tangled and simpler state, only to begin the cycle again. It’s essentially a cyclical process of a build-up of and release of energy. The sun’s magnetic field threads through the visible surface of the sun [the photosphere] and at its densest can result in the appearance of dark regions called sunspots. At solar maximum, there are many sunspots; at solar minimum, there are few or none at all.”
The next solar maximum was forecast for 2025, but the sun has been ahead of schedule this cycle, sending out higher numbers of flares and CMEs than would usually be expected two years before the maximum.
“During solar minimum, the sun has a clear bipolar magnetic field with fast and relatively undisturbed solar wind” Dorrian said. “At solar maximum the whole solar magnetic field becomes quite chaotic with a highly variable solar wind flow…and large numbers of solar flares and CMEs.”
The sun’s poles swapping is a sign that the maximum is approaching. Currently, its south magnetic pole has almost completely vanished, with the north pole just hanging on. This is expected to send ripples into the heliospheric current sheet, which will also have an impact on Earth’s space weather.
“The heliospheric current sheet is like a projection of the solar magnetic field out into space,” Billett said. “When at solar minimum, we get a somewhat predictable current sheet as the poles are well-defined, so it’s not very variable when it hits Earth. Think of it like ripples of the magnetic field hitting Earth-like waves on a beach…you get the peaks and troughs. At maximum, you still get the waves, but there is more structure and variability. The differences in the current sheet between maximum and minimum don’t have a huge impact on the Earth [compared to flares], but it does affect motions of the upper atmosphere.”
Despite its scary-sounding effects, the real-life impacts on Earth are likely to be minimal, except for the unlikely case of an exceptionally powerful flare or CME heading our way.
“Most space weather impacts for humans are technological,” Dorrian said. “Solar storms can disrupt satellite operations, and occasionally damage ground-based infrastructure. I should emphasize, however, that human civilization has witnessed and cataloged 25 solar cycles [if one includes the present one], six of which occurred in the Space Age, so we should be OK.”
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