On the observation of traveling acoustic waves in the solar atmosphere using a magneto-optical filter

In contrast to low-frequency waves that are trapped in the cavity of the Sun, high-frequency waves can travel freely in the solar atmosphere. By modelling the observed intensity signal in the red and blue wings of K I 7699 angstrom and Na I 5890 angstrom, we aim to better understand the measurements carried out with the Magneto-Optical Filter at Two Heights (MOTH) experiment. We model the observed intensity signal with radiative transfer calculations carried out with the COde for Solar Irradiance (COSI). Furthermore, we derive the formation height of the lines in order to analyze to what extent the contribution functions are modulated by the acoustic waves. We find a phase lag between the red and blue filter for acoustic waves with a frequency above approximate to 7 mHz and conclude that a frequency dependent data analysis is required for higher frequencies. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinbeim.