Poster abstract details

Although in the stellar interiors the p-mode oscillations are almost adiabatic, the motions becomes strongly non adiabatic in the atmosphere, because the thermal relaxation time is of the same order or even less than the pulsational periods. In addition, the modes may become non-linear at sufficient altitudes. In this work we aim to check upon the goodness of the adiabatic and non-adiabatic approximations of the solar oscillations by investigating the $p$-mode amplitude changes with height in the solar atmosphere. We use TH\'EMIS observations of NaD1 (5896 A) and K (7699 A) spectral lines; in fact, while formation heights of K spectral line is essentially located in the photospheric layer, the formation heights of the NaD1 line span from photosphere up to chromosphere. By analyzing power spectra obtained by temporal series at different points of the NaD1 and K spectral lines, we estimate the $p$-mode amplitude increase with height for frequencies in the range 2.5-4.5 mHz. These findings are compared with the theoretical predictions of p-mode amplitude changes obtained by adiabatic and non adiabatic models of linear stellar oscillations.