Flows and oscillations in sunspot penumbra

In observations of penumbra oscillations there is the challenging problem of separating the oscillations associated with Evershed flows from those of a different nature. The authors used the differential method which is best suited to this problem as it can be used to filter out the wave motions in the direction and wavelength already at the stage of observation. Our findings indicate that, in addition to the 10-12 min periods, periods near 30-35 minutes are present in the velocity variations of Evershed flows. Furthermore, the possible candidates for this role are the 8 min oscillations, which we have also observed at two height levels of sunspot penumbra.