Increasing the Visibility of Solar Oscillations

Abstract

Recent calculations by Toutain, Berthomieu, & Provost predict that low-degree p- and g-modes should produce large continuum intensity perturbations close to the solar limb. Analysis of 72 hr of spatially resolved, full-disk, continuum intensity images of the Sun--obtained with the Solar Oscillations Investigation/Michelson Doppler Imager instrument on board the Solar and Heliospheric Observatory--verifies the theoretical prediction for the p-mode signal. The p-mode amplitude for observations of the solar limb is found to be more than twice that for observations of the solar disk. In addition, the low-frequency background level is substantially reduced over that measured using a full-disk analysis. The combination of these two effects suggests that observing the solar limb signal could significantly enhance our chances of detecting g-modes and low-frequency p-modes.