Magnetic effect on wavelike properties of solar supergranulation

Supergranular convective cells on the Sun rotate faster than surface plasma or any other feature. Recent time-distance helioseismology results suggest that supergranulation has properties of traveling waves. We have suggested that these properties may be due to the steep gradient of the subsurface shear layer. We used a linear model to calculate the phase speeds of the unstable convective modes. These phase speeds are greater than the speed of the surface plasma; however, they are significantly lower than the observed speed of the supergranular pattern. This suggests to us that the subsurface shear layer is a plausible explanation for the wavelike behavior. We now investigate the contribution of the magnetic field to the wavelike behavior produced by the shear gradient, and we show that a horizontal (toroidal) magnetic field in the subsurface layer will result in an increase in the phase speed of the traveling convective modes. This prediction can be checked by an analysis of the observational data.