Centennial Gleissberg Cycle suggests solar cycles will intensify until 2055

Based on the centennial trend, researchers project that solar cycles 26, 27, and 28 will grow progressively stronger. Solar Cycle 26, peaking around 2036, could surpass the current cycle, while Solar Cycle 28, expected around 2055, may mark the Gleissberg maximum.

The dates are model-based projections, not official forecasts from the National Oceanic and Atmospheric Administration (NOAA) or the National Aeronautics and Space Administration (NASA). Still, the Gleissberg framework suggests that the 2030s to 2050s may bring the most intense solar conditions in over a century.

“With a major increase in launch rates, it will be important to plan for changes to the space environment that thousands of satellites and spacecraft are flying through from all sides,” said Kalvyn Adams of the University of Colorado, lead author of the new study. “Solar activity and particle fluxes could all be very different in the decades ahead.”

Implications for Earth and technology

A century-scale rise in solar activity has direct consequences for modern systems.

Satellites and spacecraft experience increased atmospheric drag during periods of elevated ultraviolet radiation, which shortens orbital lifespans. Radiation levels also rise, raising the risk of electronics failures and operational disruptions.

Power grids are vulnerable to strong geomagnetic storms that can induce currents in long transmission lines. In severe cases, this may result in widespread blackouts and damage to infrastructure.

Aviation and communications are affected as polar flight routes and high-frequency radio links experience interruptions during solar storms. This can lead to rerouting of aircraft and reduced reliability of global communication networks.

Auroras and the atmosphere respond to intense solar cycles with expanded activity at mid-latitudes. While this increases visibility of auroras, it also contributes to atmospheric disturbances and variability.

For a world increasingly reliant on space infrastructure, these long-term solar cycles are no longer only a scientific curiosity. They are a critical part of planning for the resilience of satellites, power systems, and communications in the decades ahead.

Evidence from the South Atlantic Anomaly

Researchers detected the turnover of the Gleissberg Cycle in the South Atlantic Anomaly, a region where Earth’s magnetic field is weakest and where satellites record unusually high radiation exposure. Adams explained,

“We have been looking at protons in the South Atlantic Anomaly,” Adams said. “These are particles from the sun that come unusually close to Earth because our planet’s magnetic shield is weak over the south Atlantic Ocean.”

NOAA’s Polar Operational Environmental Satellites (POES) have tracked trapped protons in this region for decades. From 1998 to 2021, data from NOAA-15 showed a steady increase in proton flux, consistent with reduced solar ultraviolet output during the Gleissberg minimum.

This pattern reversed abruptly in 2022. As Solar Cycle 25 intensified, F10.7 solar radio flux rose sharply. The resulting atmospheric heating expanded the upper atmosphere, increasing collisions that drained the proton population. Measurements from NOAA-15 and NOAA-19 show a steep decline in flux between 2022 and 2024.

“Protons in the South Atlantic Anomaly are a canary in a coal mine for the Gleissberg Cycle,” said Adams. “When these protons decrease, it means the Gleissberg Cycle is about to surge. That is exactly what we found.”

The decline in proton levels aligns with other signs of strengthening solar activity. Sunspot numbers are increasing more rapidly than expected, and the Sun’s ultraviolet output is rising. NOAA and NASA observations confirm that Solar Cycle 25 has already surpassed official forecasts. Taken together, these developments suggest that the Gleissberg minimum has ended and the Sun is moving into a stronger phase.

The long rhythm of the Gleissberg Cycle

Solar activity is most often described by the 11-year sunspot cycle. Over longer timescales, this cycle is modulated by the Centennial Gleissberg Cycle, which spans about 80 to 100 years.

German astronomer Wolfgang Gleissberg first described this pattern in 1939, noting that sunspot activity tends to weaken during its minima and strengthen during its maxima. The cycle extends across several 11-year periods, producing decades-long variations in overall solar strength.

For about 15 years, the sun remained near a Gleissberg minimum. This included Solar Cycle 24, which peaked in April 2014 with the lowest smoothed sunspot count in over a century. New evidence now confirms that this extended low phase has ended, and solar activity is climbing again.

Joan Feynman’s enduring insight

The late Joan Feynman, was among the most influential researchers connecting long-term solar variability to Gleissberg modulation. In a 2014 study with Tatiana Ruzmaikin, she argued that Solar Cycle 24 coincided almost perfectly with the Gleissberg minimum, explaining its unusual weakness.

Feynman insisted that the centennial oscillation was not only a historical curiosity but an active driver of modern solar behavior. The new data now validate her view, showing that the Gleissberg minimum has passed and the upward swing she anticipated is beginning.

References:

¹ Turnover in Gleissberg Cycle Dependence of Inner Zone Proton Flux – Kalvyn Adams et al. – March 2, 2025 – https://doi.org/10.1029/2024SW004238 – OPEN ACCESS

² The Centennial Gleissberg Cycle – Space Weather Archive – September 18, 2025

Reet Kaur

I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.

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