The study of the Sun's interior by observing the oscillations of its surface. Solar oscillations occur on both a global and a local scale. Local oscillations are apparent through small Doppler shifts in photospheric absorption lines at different places on the Sun's disk. The period of the waves averages 5 min, with maximum velocities of about 0.5 km/s. Typically, a pattern of oscillations appears over a few thousand kilometres and persists for 30 min. The oscillations are due to the superposition of many standing sound waves, or p modes, which travel around the Sun between the surface and relatively shallow layers of its interior. Global oscillations are observed by the Doppler shifts in photospheric absorption lines in the Sun's integrated light. Such large-scale oscillations are due to p modes which travel from the Sun's surface to the deepest parts of the interior; the oscillation period averages 5 min, with a range of about 4–8 min.
Subjects: Astronomy and Astrophysics.