Variation of the frequencies of very low L p-modes

Radial velocity observations performed using a resonant scattering instrument from 1980 to 1993 at the Observatorio del Teide have been used to calculate the monthly power spectra of very low degree solar oscillations. Cross-correlations among the spectra allow to determine the p-mode frequency shifts along the observed period. These shifts show a clear correlation with several indices of solar activity along the 11 years cycle but, on shorter timescales, the correlation is not clear. As the size of the effect is approximately 30% higher than the one found found using high degree modes, other phenomena (probably related to magnetic fields) possibly occurring in the interior of the Sun may be involved in these solar cycle-related frequency shifts.