Formation of Near-Surface Magnetic Fields of the Sun

In this work, we studied the formation of a large-scale magnetic field. For this, we used the surface flux transport (SFT) model. We have studied the model's accuracy and its sensitivity to uncertainties in its key parameters and input data. We also compared the simulated magnetic field with observations of the SDO/HMI and STOP/Kislovodsk magnetic fields. Overall there is good agreement between the simulations and observations. Although the model cannot reproduce fine details of the magnetic field, the long-term evolution of the polar field is very similar in simulations and observations. During even one activity cycle, large-scale field drift waves to high latitudes change polarity. Magnetic field drift waves, the sign of which corresponds to the magnetic polarity of the trailing parts of the active regions, often exist during the decline phase of activity. This does not quite correspond to the idea of mutual compensation of the leading fields of active regions across the equator. We also looked at the magnetic field flux across the equator. We confirmed that the flux across the equator does not show a clear predominance of leading sunspot polarity. The results are discussed to test dynamo models.