TEMPORAL CHARACTERISTICS OF SOLAR P-MODES

A method for ''time/frequency'' analysis is shortly described, with a discussion of its limitations in time and frequency resolution, and in sensitivity to noise in the signal. This is then applied to observati onal data. The data used are the luminosity measurements of the IPHIR experiment, and the velocity measurements performed at the Observatori o del Teide. The application to these two contemporary data sets confi rms the reliability of the method and provides additional proof that t he observed variation with time is not an effect of noise. The long an d continuous data set allows to extract information on the temporal be haviour of low degree solar p-modes. The power of the modes is shown t o vary strongly over a time-scale of a few days. These estimates are d irect measurements from power variations, unlike those deduced from wi dth measured in Fourier spectra. The temporal behaviour of several mod es are compared, mainly showing independent behaviour, but also giving some indications of weak correlations between neighbouring modes.