Authors: Krishnendu Mandal (New Jersey Institute of Technology), Alexander G. Kosovichev (New Jersey Institute of Technology, NASA Ames Research Center),Valery V. Pipin (Institute of Solar-Terrestrial Physics)

Solar differential rotation exhibits a prominent feature: cyclic variations over the solar cycle, known as zonal flows or torsional oscillations, observed throughout the convection zone. Given the challenge of measuring magnetic fields in subsurface layers, understanding deep torsional oscillations is pivotal for deciphering the underlying solar dynamo mechanism. In this study, we address the critical question of identifying specific signatures within helioseismic frequency-splitting data associated with these oscillations.

To achieve this, we employ a comprehensive forward modeling approach to simulate helioseismic data for a dynamo model that partially reproduces solar-cycle variations of magnetic fields and flows. By analyzing the simulated splitting coefficients with realistic noise, we demonstrate the possibility of identifying the dynamo wave-like signature present in the solar zonal flow from the tachocline to the solar surface. We then apply our formalism to observed data from MDI, HMI, and GONG.

Our analysis reveals a similar dynamo wave-like signature in the observed solar zonal flow. This signature migrates slowly from the tachocline to the surface at low latitudes (<30 degrees) and very rapidly at high latitudes (>45 degrees). This finding validates earlier detections of dynamo waves and holds significant implications for solar dynamo theory models.