Temporal variation of the observed Fe i 6301.5 Å line core position. The oscillatory evolution is displayed for two 20 min-sequences observed in the Quiet Sun. Left panel: measured on October 14 2016 at 09:34 UT at the heliocentric parameter μ = 0.9 on the southern axis of the solar meridian. Right panel: october 13 2016 at 15:07 UT at μ = 0.8 on the northern axis of the meridian. The single measurements (asterisks) have a cadence of 1.5 s. The left y-axes scale the wavelength in Å, the right y-axes are the translated Doppler velocities in m s^-1.