Authors: Krishnendu Mandal (New Jersey Institute of Technology), Alexander G. Kosovichev (New Jersey Institute of Technology)

The precise location of the solar dynamo remains an open question: whether it is concentrated in the near-surface shear layer, distributed throughout the convection zone, or generated near the tachocline — the sharp rotational transition layer at the base of the convection zone, roughly 200,000 km below the solar surface. Previous studies have provided support for each of these scenarios. In particular, the solar magnetic butterfly diagram and the pattern of zonal flows, known as torsional oscillations, show remarkable similarities, indicating a close connection between magnetic field evolution and large-scale solar flows. Because magnetic fields cannot be directly measured deep inside the Sun, torsional oscillations and rotational gradients serve as important diagnostic proxies. Our analysis shows that the rotational gradient near the tachocline exhibits butterfly-like patterns closely resembling the surface magnetic butterfly diagram. These findings favor a deep-seated origin of the solar dynamo, operating either near the tachocline or throughout the convection zone, and argue against recent shallow, near-surface dynamo models. The results may also provide broader insight into the operation of stellar dynamos in general.