A FOURIER SPECTRUM ANALYSIS OF LONG SAMPLES OF SOLAR LINE OSCILLATIONS

Sequences of the oscillations of solar lines up to 2 hours 20 min long have been recorded at the same point on the sun. The power spectra show several peaks separated by 0.85 × 10-3 cps on average from each other. A sharp main peak at 3.3 × 10-3 cps (300 sec period) is almost always present. These results suggest that the lifetime of the phase of the oscillation is much longer than that of the amplitude and is likely to exceed one hour. We actually observe the modulation of a wave in smaller wave trains about 11 min long and 20 min apart (average values). Observations with low spatial resolution also suggest that the area of coherence is much greater for the phase than for the amplitude. © 1969 D. Reidel Publishing Company.