An Observational Search for Solar Pulsations at Periods from Seven to Seventy Minutes.

摘要

The large-scale solar velocity field has been measured by comparing Doppler shifts from the center and limb of the disk, using the non-magnetic line FeI 5123.730A. No statistically significant periodicities are observed at periods between seven and seventy minutes. This negative result agrees with other results obtained by observers using spectral techniques, and contrasts with the report of oscillations at similar periods by Hill and co-workers (Hill et al., 1976a; Brown et al., 1976). Hill's explanation of this apparent discrepancy is that his instrument has a greatly enhanced sensitivity to one of two possible modes of oscillation. Independent modeling of the sun's atmosphere confirms that the FFTD technique would have much greater sensitivity to one of the two modes. However, it is concluded that this mode cannot be present in sufficient quantity to explain the apparent discrepancy because of the structure of the sun's atmosphere and because of comparisons of velocity and temperature measurements at different levels of the atmsophere. In addition, questions are raised concerning the statistical significance of the peaks in the SCLERA power spectra.