DARK LANES IN GRANULATION AND THE EXCITATION OF SOLAR OSCILLATIONS

We made simultaneous, high-resolution observations of the Sun's granulation and solar acoustic events in the photosphere. We find that the acoustic events, which are a local by-product of the excitation of solar oscillations (Goode, Gough, and Kosovichev 1992), occur preferentially in the dark, intergranular lanes. At the site of a typical acoustic event the local granulation becomes darker over several minutes leading up to the event with a further, abrupt darkening immediately preceding the peak of the event. Further, the stronger the acoustic event the darker the granulation. Thus, the excitation of solar oscillations seems more closely associated with the rapid cooling occurring in the upper convection layer, rather than the overshooting of turbulent convection itself. We find no substantial role for so-called ''exploding'' granules in the excitation of solar oscillations.