Oscillations in the photosphere of a sunspot umbra from the inversion of infrared Stokes profiles

We report on the detection of magnetic field strength and velocity oscillat ions in the photosphere of a sunspot umbra. Our analysis is based on the in version of the full Stokes vector of three Fe I lines at 15650 Angstrom fro m which the stratification with optical depth of the different atmospheric parameters has been derived. This allows us to estimate the amplitude of th e oscillations and the phase lag between the fluctuations in the line-of-si ght velocity and held strength. Our results suggest that the inferred magne tic field oscillations are caused by opacity fluctuations that move upward and downward the region where the spectral lines are sensitive to magnetic fields.