Speaker
Description
Solar magnetic activity is very crucial to understand as it mediates all aspects of space weather. The most successful dynamo model to explain various features of the solar magnetic cycle (e.g., equatorward migration of sunspots and 11-year periodicity) is the Babcock-Leighton Dynamo model. In this dynamo model, we solve kinematic MHD equations by providing the observed mean flows of the Sun to understand various magnetic features including the 11-year solar cycle. However, many turbulent transport parameters inside the convection zone of the Sun are not well constrained observationally but assumed appropriately based on theoretical understanding to reproduce surface observations. In this present work, we assimilate full disc MDI and HMI daily magnetogram data observed from 1996-2024 in the 3D Flux Transport dynamo model to understand the internal dynamics of the magnetic field inside the solar convection zone. As the far side of the Sun is not visible in the magnetogram, we follow a technique where the daily emergence of sunspots near the visible side including diffuse fields are included. The assimilated surface magnetic fields are being transported to the pole by surface meridional circulation and further to the bottom of the convection zone to generate the toroidal field due to differential rotation. We are successfully able to reproduce the observed polar field and polarity reversal due to the realistic decay of surface magnetic fields. We are also able to find the correct polarity of the toroidal field and cycle reversal. The toroidal field strength computed from our model is consistent with the value of flux-emergence simulations for a specific value of turbulent diffusion which allows us to constrain its value in the convection zone. The different cyclic asymmetries including cycle strength are also reproduced. This is the first time a dynamo model is successfully able to reproduce the cyclic activity of a toroidal field deep inside the convection zone from the observed photospheric magnetogram data.
