The Sun is undergoing long-term transformations, as identified by an international research team coordinated by the University of Birmingham. Experts have detected a significant compression across the last four solar activity cycles. This could indicate that our star is transitioning into a new behavioral pattern.
A new study, published in the Monthly Notices of the Royal Astronomical Society, suggests that solar magnetic activity currently resides within a thin layer situated just beneath the Sun’s surface. This points to a profound alteration in the Sun’s active rhythm.
Its eleven-year cycles of activity fluctuate between periods of low intensity and times marked by explosive events, such as charged particle bursts and coronal mass ejections. These events are the primary drivers of space weather hazards. Beneath the star’s surface, processes generating the magnetic field that governs solar cycles are underway, and these cycles, in turn, create space weather. The latter can pose extreme dangers to electronic and communication infrastructure, including GPS systems and power grids.
As reliance on such infrastructure continuously grows, the accuracy of space weather forecasts becomes increasingly critical. Until recently, scientists primarily used external indicators, such as sunspots, to monitor solar activity, yet the majority of crucial processes occur below its surface.
To track these internal occurrences, researchers employed helioseismology, a method that detects subtle sound waves within the Sun’s interior. These waves act as markers for barely perceptible changes beneath the surface, offering a different perspective on recent solar cycles compared to what external observations reveal. The research draws upon helioseismic data gathered over four decades by the Birmingham Solar Oscillations Network (BiSON), which comprises six telescopes located globally.
The scientists have amassed sufficient data for comparative analysis. In processing this data, the international team identified a slow but escalating shift in the structure of the Sun’s interior, observed across several cycles. The study’s authors explain that the Sun possesses its own “active rhythm,” which generates waxing and waning magnetic activity, thereby shaping space weather. However, traditional surface measurements do not provide a complete picture.
It appears the Sun is entering a different mode of operation, characterized by magnetic activity becoming increasingly confined near the surface with each successive cycle. This is a significant and novel finding, made possible by the extensive long-term observations from BiSON.
From 1987 to 2025, spanning cycles 22 through 25, shifts in p-mode oscillations have revealed internal changes within the Sun. These changes have become particularly pronounced starting with the 23rd cycle, with more alterations occurring near the surface, at depths less than 1,000 kilometers. In the most recent, 25th cycle, helioseismic data indicate a substantial structural reorganization beneath the Sun’s surface.
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