Depth of excitation and reversal of asymmetry of low- solar p modes: a complementary analysis of BiSON and VIRGO/SPM data

Abstract

We use the solutions to a simple, one-dimensional wave equation – which is intended to describe the essential elements of the solar resonant acoustic cavity – as formalistic models to which to fit low-l modes in observational helioseismic power spectra. We have analysed data collected in velocity, by the ground-based Birmingham Solar-Oscillations Network (BiSON), and in intensity, by the full-disc VIRGO Sun photometers (SPM) on board the ESA/NASA SOHO satellite. Our analysis extracts, as a function of the modal radial overtone number n, direct estimates of: the location of the excitation source of the acoustic resonances; and the size of the component of the convective granulation that is correlated to the observations of the resonances, and is responsible for the reversal of asymmetry of the mode profiles when different observation techniques are applied (i.e. intensity or Doppler velocity measurements). This information is coded in the complicated forms of the observed, resonant profiles.