Solar “Switch‑Off” Point Unlocks Early Forecasts for Cycle 26

When the Sun quiets down after a burst of powerful storms, it leaves behind a subtle clue – a so‑called “switch‑off” point. It sounds almost poetic, but for solar physicists it’s a hard‑won data marker that could change how we predict the Sun’s next mood swing.

Prof. Sandra Chapman of the University of Warwick, who’s best known for her work on planetary magnetic fields, explains that the moment extreme geomagnetic events cease marks the Sun’s magnetic bands sliding together near the solar equator. Once that happens, the Sun’s future activity becomes far easier to read.

Using this insight, Chapman’s team published a paper in The Astrophysical Journal (May 22 2026) that outlines a “declining‑phase precursor.” The method looks back at the tail‑end of the current cycle – Cycle 25 – and, by noting when the most severe space‑weather episodes stop, projects the size and timing of the next cycle.

According to the model, Solar Cycle 26 will likely be a “moderate” one, with a maximum sunspot number somewhere between 100 and 120. In plain English, that’s about the same level as the recent Cycle 25, perhaps a little weaker. The real kicker? The forecast can be made six to seven years before the cycle peaks – roughly a decade before the Sun reaches its busiest phase.

This early warning could be a game‑changer for operators of satellites, power grids, and even airline routes that have to contend with sudden solar‑induced disruptions. While the exact amplitude of the cycle won’t be nailed down until a couple of years after the switch‑off point (around 2028‑29), the broad envelope is now in sight.

Back in May 2024, a handful of surprisingly strong storms lit up the night sky as far south as Devon and Cornwall, reminding us how quickly space weather can turn unsettling. Those events were among the last of Cycle 25’s extreme episodes, and their cessation helped define the switch‑off moment that underpins Chapman’s forecast.

Beyond the science, the discovery has earned Chapman a fresh round of accolades, including the Royal Astronomical Society’s Chapman Medal in 2022 for her contributions to space‑weather research. As the solar community digests this new tool, many are already looking ahead – hoping the Sun’s next quiet spell will give us the lead‑time we need to protect our modern, technology‑dependent world.