Oscillations in Sunspots observed in the Near Infrared

Spectropolarimetric time series of two sunspots are investigated to search for magnetic field oscillations. While the existence of velocity oscillations in the five-minute band is clearly confirmed, periodic variations of the magnetic field strength or the magnetic angles inclination and azimuth are small and restricted to very narrow areas. They occur in single frequency bins, but different for magnetic field strength and angles. Small dark structures embedded in one penumbra or in the near surroundings of the other spot exhibit enhanced power for the magnetic variations at all frequencies. Phase differences are rather unsure. The obtained values are in agreement with intrinsic magnetic field variations produced by slow magnetoacoustic modes as well as with an opacity mechanism connected with fast modes.