Acoustic wave propagation in the solar atmosphere. II. Nonlinear response to adiabatic wave excitation.
Abstract
We study the response of the solar atmosphere to excitations with adiabatic large amplitude acoustic waves. Both monochromatic waves and acoustic spectra are considered. For monochromatic excitation a critical frequency ν_cr_ is found which separates different domains of resonance behaviour. Upon excitation with frequencies ν<ν_cr_ the atmospheric resonance decays rapidly with time as in the small amplitude wave case, while for ν>ν_cr_, persistent resonance oscillations occur which are caused by shock overtakings. Excitation by acoustic spectra always leads to the ν>ν_cr_ behaviour. Independent of the spectral shape and energy, acoustic spectra generate oscillations mainly at frequencies ν=6-7mHz at the top of the chromosphere. The photospheric 5-min oscillation does not influence our chromospheric results. Shock heating by acoustic spectra is roughly similar to that of a monochromatic wave of period 35s. Irrespective of the initial spectral shape and energy and even of the gravity and effective temperature of the star, a universal average shock strength M_S_=1.5 is found. Due to our adiabatic treatment, the atmospheric slabs suffer extension which grows with wave energy.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 1995
- Bibcode:
- 1995A&A...294..241S
- Keywords:
-
- HYDRODYNAMICS;
- SHOCK WAVES;
- WAVES;
- SUN: CHROMOSPHERE;
- SUN: OSCILLATIONS