The Sun's Two Pendulums: How Coupled Oscillations Create a 90-Year Rhythm
Place two pendulums side by side and give one a gentle push; the other will soon pick up the rhythm. This behavior isn't limited to clocks on a shared shelf; it also applies to the plasma inside the Sun. In the star's convection zone, two huge ring-shaped flows circulate: one closer to the surface, the other deeper. Each oscillates with its own period—12.05 and 9.52 years.