Helioseismology Finds Solar Magnetic Activity Shifting Toward the Surface

An international team led by the University of Birmingham, using 40 years of BiSON observations (1987–2025, solar cycles 22–25), found that changes tied to the Sun's magnetic activity are increasingly confined to layers within 1,000 km of the surface. The result points to a structural reorganization of internal processes rather than simply weaker magnetic fields.

• BiSON data span 1987–2025 and solar cycles 22 through 25
• The link between oscillation frequencies and surface activity changed markedly since Cycle 23
• Structural changes are confined to within 1,000 km of the surface
• Cycle 25 looks weaker in surface indicators but high-frequency oscillations match earlier cycles