The acoustic overstability in a polytropic plane-parallel atmosphere with superadiabatic temperature gradient and radiative dissipation is demonstrated for optically thick disturbances. The periods of oscillation are found to be in the range 250-480 s and the associated wavelength of the order of 40
Solar seeing and the spatial properties of the five-minute oscillations
β Scribed by John H. Thomas
- Publisher
- Springer
- Year
- 1972
- Tongue
- English
- Weight
- 625 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0038-0938
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β¦ Synopsis
A numerical simulation of observations of the spatial properties of the five-minute oscillations is carried out, assuming the oscillations are internal gravity waves excited by granular convection according to the theory of Thomas et al. (1971). The simulation includes the effects of seeing and finite aperture. The details of the simulation are chosen to model the observational method of Frazier (1968a, b). The results show that the peak in the observed power spectrum of the oscillations can occur at a wavelength considerably longer than the true wavelength of the oscillations. In particular, the peak in Frazier's observed power spectra at wavelength 2 ~ 5000 km is consistent with the considerably shorter true wavelength 2 ~ 1500 km predicted by the gravity wave theory.
π SIMILAR VOLUMES
The 5-min oscillations in the photospheric velocity fields have been studied in detail from measurements on 14 absorption lines from three time sequences of spectrograms of high quality. The lines cover a range of heights in the solar atmosphere from log z = + 0.2 to --1.2. Regions oscillating coher