Rotational shear near the solar surface as a probe for subphotospheric magnetic fields

Abstract

Helioseismology revealed an increase in the rotation rate with depth just beneath the solar surface. The relative magnitude of the radial shear is almost constant with latitude. This rotational state can be interpreted as a consequence of two conditions characteristic of the near-surface convection: the smallness of convective turnover time in comparison with the rotation period and absence of a horizontal preferred direction of convection anisotropy. The latter condition is violated in the presence of a magnetic field. This raises the question of whether the subphotospheric fields can be probed with measurements of near-surface rotational shear. The shear is shown to be weakly sensitive to magnetic fields but can serve as a probe for sufficiently strong fields of the order of one kilogauss. It is suggested that the radial differential rotation in extended convective envelopes of red giants is of the same origin as the near-surface rotational shear of the Sun.

5 pages (two columns), 4 figures, to apper in Astronomy Letters

References in corpus (3)

• The case for a distributed solar dynamo shaped by near-surface shear
• The radial gradient of the near-surface shear layer of the Sun
• Lambda-effect from forced turbulence simulations

Cited by in corpus (11)

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• Effects of a subadiabatic layer on convection and dynamos in spherical wedge simulations
• Changes in the near-surface shear layer of the Sun
• Magnetic and rotational quenching of the $\Lambda$ effect
• Solar-cycle variation of the rotational shear near the solar surface
• Solar-cycle variations in meridional flows and rotational shear within the Sun's near-surface shear layer
• Small-scale and large-scale dynamos in global convection simulations of solar-like stars
• Magnetorotational instability in a solar near-surface mean-field dynamo
• Generation of mean flows in rotating anisotropic turbulence: The case of solar near-surface shear layer
• Modelling differential rotation of red giants: the case of the evolved sun