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Solar scientists have detected signs that the next solar cycle has begun. This is despite the fact that there are still six more years to wait and the current solar cycle (Cycle 25) is still ongoing.
The current solar cycle is expected to reach its peak, or “solar maximum,” in mid-2025, when our star’s magnetic field will reverse and its poles will switch. Leading up to this solar activity has been increasing, with an increase in sunspots, solar flares, and stellar plasma ejections called coronal mass ejections (CMEs).
While Cycle 25 has reached its peak, it looks like Cycle 26 is just itching to join in. The rumblings of the start of the next 11-year solar cycle came in the form of “starquakes” – sound waves bouncing off the sun’s interior – which were detected by researchers at the University of Birmingham.
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“It’s exciting to see the first hints that the same pattern will repeat itself in Cycle 26, which is expected to begin in about six years,” team leader Rachel Howe from the University of Birmingham said in a statement.
Wait your turn, Cycle 26!
To detect signs of this overzealous solar cycle, Howe and his colleagues used a scientific technique called “helioesismology,” which measures starquakes on our star.
Just as seismologists can use seismic waves from Earth to determine the internal structure and composition of our planet, helioseismologists can do the same with sound waves and the sun.
Helioseismology can also determine how the sun rotates. The sun is a ball of superheated gas, or plasma, so it doesn’t spin like a solid body. Instead, it experiences a form of rotation called “differential rotation,” which sees different layers of the sun moving at different angular speeds.
This creates a visible pattern of bands called “solar torsional oscillations,” some rotating faster, some slower. During the solar cycle, these bands move toward the sun’s poles and equator. The faster-rotating belts usually appear as the next sun is about to begin.
The University of Birmingham team saw faint signs of Cycle 26 becoming apparent in the spin band data they analysed.
“If you go back one solar cycle on the plot — 11 years — you can see something similar that seems to join the pattern we saw in 2017. This has become a feature of the current solar cycle, Cycle 25,” Howe said. “We’re probably seeing the first traces of Cycle 26, which won’t officially begin until about 2030.”
NASA’s Solar Dynamics Observatory (SDO) has been observing the sun since 2010, collecting helioseismic data using its onboard Helioseismic and Magnetic Imager (HMI) instrument to help scientists like Howe study solar torsional oscillation signals.
In addition, the researchers have similar data dating back to 1995, thanks to the Michelson Doppler Imager (MDI) at the Solar and Heliospheric Observatory (SOHO).
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This means Howe and his colleagues have an idea of the ascending phases of Cycles 23, 24 and 25. In fact, Howe has been tracking changes in the sun’s rotation for about 25 years, starting his research when scientists had only a fraction of the data from Cycle 23.
This revealed fast-moving material and sunspots moving toward the sun’s equator, a pattern that repeated itself in similar ways during Cycle 24 and the waxing of Cycle 25. Now, Howe has hints that the same pattern is happening again ahead of Cycle 26.
“I hope that with more data, we can understand more about the role these flows play in the complex dance of plasma and magnetic fields that make up the solar cycle,” he concluded.
The team’s research was presented at the Royal Astronomical Society’s National Astronomy Meeting 2024 (NAM 24), held in Hull.