Why does the sun's torsional oscillation begin before the sunspot cycle?

Area of Science:

• Solar physics
• Heliophysics
• Astrophysics

Background:

• The Sun's torsional oscillation is thought to be driven by the Lorentz force linked to the sunspot cycle.
• However, observations show this oscillation begins 2-3 years prior to the sunspot cycle.
• This temporal discrepancy requires a theoretical explanation.

Purpose of the Study:

• To provide a theoretical explanation for the observed 2-3 year lead of torsional oscillations over the sunspot cycle.
• To investigate the role of meridional circulation in the solar dynamo.
• To understand the formation of the toroidal magnetic field in the Sun.

Main Methods:

• Utilized a solar dynamo model.
• Incorporated meridional circulation penetrating below the convection zone.
• Analyzed the formation timing and latitude of the toroidal magnetic field.

Main Results:

• The solar dynamo model successfully reproduced the torsional oscillation preceding the sunspot cycle.
• The model demonstrated that the strong toroidal field forms a few years before the sunspot cycle.
• This toroidal field formation occurs at higher latitudes than previously assumed.

Conclusions:

• The proposed solar dynamo model with deep meridional circulation provides a viable explanation for the torsional oscillation's early onset.
• The timing and location of toroidal field generation are crucial for understanding the solar cycle dynamics.
• Further research can refine these models to better predict solar activity.