Fine structure of wave motions in the solar photosphere: Observations and theory

Spectral observations of the 639.361-nm FeI line at the center of the quiet solar disk with high spatial (0.4″) and temporal (10 s) resolution are used to investigate the behavior of local 5-min oscillations over granules and intergranular lanes. The power of the 5-min oscillations in the upper photosphere (at heights of H ≈ 490 km) is higher the faster the convective motions in the lower photosphere (H ≈ 10 km). This suggests that turbulent convection is responsible for the excitation of local solar oscillations. A statistical analysis of the oscillations shows that, on average, both the intensity and velocity of the oscillation amplitudes are greater over intergranular lanes. This difference in amplitudes is present throughout the studied heights in the photosphere (H = 0−490 km). The period at which the power spectrum of velocity oscillations reaches its maximum is longer over intergranules than over granules. Simulations of the propagation of acoustic-gravity waves in an atmosphere taking into account the convection pattern give a satisfactory explanation for the above observed effects. It is concluded that the atmospheric modulation of the 5-min oscillations is an additional or alternative mechanism responsible for differences between these oscillations over granules and intergranules.