Disk‐integrated Intensity Pseudomodes Measured by SOHO /VIRGO

Abstract

The high-frequency spectrum above the acoustic cutoff frequency ($ν$ac) of the solar atmosphere has been observed in velocity measurements at low and high angular degrees and reveals significant evidence for the presence of pseudomodes characterized by their equally spaced signal. In this paper we study this region of the spectra using for the first time disk-integrated intensity measurements from the VIRGO/SPM photometers on board the SOHO probe. These pseudomodes have high visibility, and whereas the frequency separation between the pseudomodes is the same, some differences are found among the three wavelengths. We have studied the evolution of the pseudomodes with the solar cycle; nevertheless, no significant variations are found. Finally, the intensity pseudomodes of VIRGO/SPM are compared with those of velocity as seen by the GOLF instrument during the same periods and with the same analytical techniques.