Rotational Splitting of Solar Five-Minute Oscillations of Low Degree

Abstract

An analysis of 28 contiguous days of whole disk observations of the solar surface by means of optical resonant scattering in the K 769.9 nm line, taken at the Teide Observatory at Izana during July–August 1980, have thus far yielded two significant facts. Firstly when the results of an iterative sine-wave fitting procedure are considered in the period range 2–3 h, although the expected daily harmonics corresponding to 1/8, 1 / 10, 1/11, and 1 / 12 of a day are clearly seen the 1 /9th contribution is significantly absent. It is suggested that this results from an interference between a signal of 160 min (1/9th of a day) with the daily harmonic. It is further pointed out that the observatories at which the 160 min oscillation has been seen, Crimea, Pic du Midi, and Stanford are all separated by integral numbers of 160 min, and thus the phase of the 160 min oscillation relative to the daily observation window is constant. However, the Teide Observatory is situated at a half integral number of 160 min periods relative to the others. Thus when constructive interference exist at the first three sites destructive interference will exist at the latter. It is thus concluded that the non-existence of a peak corresponding to the 1/9th harmonic of a day in the sine-wave fit data is strong indirect evidence for the existence of the 160 min signal.

Proceedings of the 66th IAU Colloqium: Problems in Solar and Stellar Oscillations, held at the Crimean Astrophysical Observatory, U.S.S.R., 1–5 September, 1981.