The Sun doesn't rotate as a solid body: its equator spins faster than its poles. This difference in rotation speed creates layers that move at different speeds, like ocean currents at different depths. Scientists have long suspected that these currents are responsible for the Sun's magnetic field, but they couldn't pinpoint exactly where it originates.
A new study used data on so-called torsional oscillations — periodic speed-ups and slow-downs of rotation at different latitudes. It turns out that the pattern of these oscillations in a deep layer, located about 200,000 kilometers below the surface, is strikingly similar to the pattern of sunspots that astronomers have observed for centuries. This layer is a transition zone between the calm core and the turbulent outer shell of the Sun.
The similarity of patterns means that the magnetic field is most likely generated in this deep zone, not near the surface, as some recent hypotheses suggested. This helps us understand not only our Sun but also how magnetic fields work in other stars.
The layer where the Sun's magnetic field may be born is located 200,000 kilometers deep — about half the distance from Earth to the Moon.