MHD waves in small magnetic elements: comparing IMaX observations to simulations.

Small-scale magnetic fields are thought to play an important role in the heating of the outer solar atmosphere. By exploiting the high-spatial and temporal resolution of IMaX, the bidimensional spectropolarimeter on board the Sunrise balloon-borne observatory, we study the excitation of MHD waves in small magnetic elements, providing clues on the interaction of the magnetic structures with the photospheric forcing and the ambient acoustic field. The large fraction of magnetic features observed by IMaX made it possible to study the interaction between the photospheric granulation and the flux tubes from a statistical point-of-view. In particular we find a 90 degree phase lag with an high confidence level between the horizontal displacements of the flux tubes and the velocity perturbations measured inside them. We also find that the observational results are in excellent agreement with MHD simulations. This result suggests that the horizontal displacement of small-scale magnetic features by the surrounding granulation excites longitudinal waves within the magnetic elements.