The solar interior and BISON observations

Extract

The data taken by the Birmingham Solar Oscillation Network (BISON) forms an interesting link between the twin themes of this session: solar and stellar seismology. Like stellar astronomers, we view the Sun as a star without spatial resolution. There are clearly disadvantages in this, in that we lose information about oscillations which vary rapidly across the Sun. But we are not limited to just the simple radial mode which has l=0; because of Doppler imaging we see modes with a range of l from 0 to 4. Unlike stellar astronomers, our star is near to us and the photon flux is high enough that we need not be limited by photon shot noise. We detect the modes by measuring the integrated surface velocity of the Sun. With long integration times, and for the coherent modes, the smallest amplitudes that we can measure are between 1 and 0.1 cm s⁻¹.