A thin transition layer where the Sun’s rotation changes abruptly — the outer convection zone rotates differentially, while the inner radiative zone rotates almost like a solid body- is termed as the tachocline similar to the thermocline in oceanic dynamics. This sharp shear is believed to generate the Sun’s strongest toroidal magnetic fields, which later rise to the surface as sunspots. The tachocline’s sub-adiabatic stratification allows strong magnetic fields to be stored without immediately rising due to buoyancy. If the solar dynamo exists in the tachocline and generates the magnetic field of the Sun, one would expect solar-cycle related changes in the properties of the tachocline.
A recent study using three decades of GONG observations reports a secular shift in the tachocline’s position at low latitudes. The analysis also indicates that the tachocline has been gradually moving closer to the base of the convection zone, indicating that it may be related to the complexity of the solar magnetic field.
This work is published in Astrophysical journal, 1000, 272 (1000) 2026 April 1.
Latitude-dependent Time Variations of the Solar Tachocline - IOPscience
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