Photospheric Oscillations. III. Search for Long Period Modes
Abstract
Summary. The stability of the sodium optical resonance device has been optimised for the study of long period solar pulsations. Observations are made on the integrated solar light, which are insensitive to guiding errors. The residual five-minute oscillation is clearly observed with a r.m.s. amplitude of about 2 m s `. The low frequency spectrum is carefully examined in the range of periods between five minutes and 1.5 h, with a sensivity of 70 cm s `. After subtraction of the slow drifts, the data are treated by standard Fourier analysis and time correlations. It is shown that the power spectra never rise above the statistical significance level. It is concluded that solar oscillations, if they exist, must have an amplitude smaller than 70 cm s - in integrated light. Key words: sun - photosphere oscillations - long period modes
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1977
- Bibcode:
- 1977A&A....55..411G