The first rumblings of the Sun's next 11-year solar cycle have been detected in sound waves inside our home star – even though it is only halfway through its current one. This existing cycle is now at its peak, or 'solar maximum' - which is when the Sun’s magnetic field flips and its poles swap places - until mid-2025.

It affects activity on the Sun's surface, with sunspots, flares and coronal mass ejections all more rampant at solar maximum. This leads to a surge in electromagnetic energy hurtling towards the Earth and makes aurorae visible more often and at lower altitudes. The current solar cycle, named Cycle 25 because it is the 25th since 1755 when extensive recording of solar sunspot activity began, started in 2019.

It is not expected to end for another six years but the first signs that the next solar cycle is beginning have been spotted by researchers from the University of Birmingham and presented at the Royal Astronomical Society's National Astronomy Meeting in Hull.

Astronomers use the Sun's internal sound waves to measure how it rotates, making visible a pattern of bands (solar torsional oscillation) that rotate slightly faster or slower. These move towards the Sun's equator and its poles during the activity cycle. The faster-rotation belts tend to show up before the next solar cycle officially begins.

Dr Rachel Howe and her international collaborators have discovered a faint indication that the next solar cycle is starting to show up in the data they have been analysing from the rotation bands. "We're likely seeing the first traces of Cycle 26, which won't officially start until about 2030," she said.

Source: Royal Astronomical Society

Image: NASA/SDO and HMI science team/Rachel Howe