A global collaboration of scientists, spearheaded by experts from the University of Birmingham, has documented evidence of enduring shifts in the Sun’s behavior. Their findings suggest that over the past four solar activity cycles, the region of magnetic activity has notably contracted. According to their assessment, this phenomenon could signify the Sun transitioning into a new operational mode. The research indicates that the magnetic processes governing solar cycles are increasingly concentrating within a thin layer just beneath the Sun’s surface, potentially pointing to significant alterations in the star’s internal mechanisms.
Solar activity unfolds in cycles lasting approximately 11 years. During these periods, quiet phases give way to flares, bursts of charged particles, and coronal mass ejections. These are the very events that shape space weather, which can impact the functioning of satellites, power grids, and communication systems. To investigate what occurs beneath the Sun’s surface, researchers employed the technique of helioseismology. This method allows for the analysis of sound waves traveling within the star, providing insights into its internal structure. Unlike conventional observations focusing on sunspots and other external indicators of activity, this approach offers the ability to detect changes in deeper layers.
The foundation for this work was built upon nearly 40 years of observations gathered by the Birmingham Solar Oscillations Network (BiSON). This network comprises six telescopes situated at various locations worldwide. This extensive data archive enabled scientists to track the evolution of the Sun’s internal processes across multiple activity cycles. As detailed in a publication in the journal Monthly Notices of the Royal Astronomical Society, it was precisely the duration of these observations that facilitated the identification of this trend. The analysis revealed a gradual yet consistent shift in the structure of the Sun’s interior.
Professor Bill Chaplin of the University of Birmingham, the lead author of the study, remarked that the Sun possesses its own “active biorhythm” that dictates the waxing and waning of magnetic activity. He emphasized that focusing solely on surface observations does not provide a complete picture.
According to the researchers, the collected data point to systematic alterations within the solar cycle. With each successive cycle, magnetic activity is becoming more noticeably concentrated closer to the star’s surface. The authors stress that this particular finding was achieved for the first time thanks to the multi-year observations from the BiSON network.
An examination of the period from 1987 to 2025, encompassing 22-25 solar activity cycles, unveiled internal changes detectable in p-mode oscillations. The scientists identified three groups of oscillations at different frequencies, each associated with a specific depth of penetration beneath the Sun’s surface. Beginning with the 23rd cycle, helioseismological data started to notably diverge from the pattern indicated by external signs of activity. The researchers determined that an increasing proportion of processes are concentrating in layers located less than 1000 km from the surface. This tendency was particularly evident in the current, 25th cycle. In the opinion of the specialists, such changes cannot be solely attributed to a simple weakening of magnetic fields, suggesting that a more profound restructuring of the Sun’s internal architecture may be underway.
The study’s authors believe that continued observations during the 26th solar cycle will help ascertain whether this represents a long-term shift in the nature of solar activity. They anticipate that ongoing monitoring will allow for a more precise determination of the mechanisms that influence space weather and its impact on Earth’s technological infrastructure.
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