The Sun’s 11-year cycle still drives flares, aurorae, and geomagnetic storms, but the machinery under that familiar rhythm may be changing in a deeper way. After tracking sound waves inside the Sun for nearly four decades, researchers say its magnetic activity now appears to be packed into a thinner layer just below the visible surface. That matters because the solar cycle is the engine behind the space weather that can interfere with satellites, GPS, communications, and power grids on Earth. The new analysis, published in Monthly Notices of the Royal Astronomical Society, used observations from the Birmingham Solar Oscillations Network, or BiSON, a set of six telescopes around the world that has monitored the Sun since the late 1980s. Instead of focusing only on sunspots or radio emissions, the team listened to the Sun’s internal oscillations, tiny pressure waves known as p modes, to see how the star’s interior has changed from solar cycle 22 through cycle 25. Professor Bill Chaplin of the University of Birmingham, the study’s lead author, said: “The Sun has its …