A multi-instrument investigation of the frequency stability of oscillations above the acoustic cut-off frequency with solar activity

Below the acoustic cut-off frequency, oscillations are trapped within solar interior and become resonant. However, signatures of persist above these travelling waves known as pseudomodes. Acoustic oscillation frequencies to be correlated with cycle, but pseudomode predicted vary in anti-phase. We have studied variation time systematically through cycle. analyzed Sun-as-a-star data from Variability Solar Irradiance Gravity Oscillations (VIRGO), Global at Low Frequencies (GOLF), well decomposed Oscillation Network (GONG) for harmonic degrees $0\le l \le 200$. The cover over two cycles (1996--2021, depending on instrument). split them into overlapping 100-day long segments focused frequency ranges, namely $5600$--$6800\,\rm\mu Hz$ $5600$--$7800\,\rm\mu Hz$. shifts between were then obtained by fitting cross-correlation function segments' periodograms. For VIRGO GOLF, we found no significant activity. agreement previous studies, that variations anti-phase cycle GONG data. Furthermore, showed a double-peak feature their maximum, which corresponds activity minimum, is not seen proxies. An, yet unexplained, pseudo-periodicity amplitude degree $l$ also observed