Influence of the solar atmosphere on the p-mode eigenoscillations

An asymptotic theory of global adiabatic p-modes is developed, taking into account the influence of the solar atmosphere. It is shown that waves of the whole frequency range nu approximate to 2-10 mHz may reach the chromosphere-corona transition region (CCTR) by means of a tunneling through the atmospheric barriers. The primary acoustic cavity inside the Sun becomes considerably extended by this way, leading to a change of frequencies: low frequencies are increased, while high frequencies are decreased. The transition from low p-mode frequencies to high peak frequencies (nu greater than or similar to 6 mHz) is smooth. The locations of the turning points are determined from the wave equation for div (.) (v) over right arrow. It is shown that the internal turning point of the acoustic cavity is strongly shifted toward the center of the Sun, while the upper turning point is shifted from the surface to CCTR. That means, the turning points cannot be located in the convective zone. A new complex integral dispersion relation for the eigenfrequencies is derived. The imaginary parts of the frequencies indicate a decay of the amplitudes, resulting from considerable energy losses by tunneling from the main cavity. It is shown that waves with a decaying amplitude (complex frequency) may exist in a limited area only, penetration of linear p-modes to the corona is impossible. The CCTR acts as a free surface. We conclude that the p-modes may drive forced surface gravity waves at this surface.