Variation of Acoustic Power with Magnetic Field as Seen in Gong+ Data

The acoustic spectra in sunspots are known to be richer in higher frequency power. We have attempted a generalized study of the effect of magnetic fields on the shape of the acoustic spectrum using GONG+ bread-board data (spatial scale of ∼ 2 arc-sec per pixel) of 11 May, 2000 and 12 June, 2000. The mean power spectra of the velocity oscillations were obtained by averaging over several spectra for different values of the magnetic field. With increasing magnetic field, the acoustic power increases at higher frequencies and decreases at lower frequencies with a transition at ≃ 5 mHz. This behaviour is slightly different from earlier results obtained from SOHO/MDI data.