Open AccessAcoustic interferometry of the solar atmosphere: p‐modes with frequencies near the ‘acoustic cut‐off’
Author(s) -
Vorontsov S. V.,
Jefferies S. M.,
Duval, Jr T. L.,
Harvey J. W.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01630.x
Subject(s) - physics , photosphere , atmosphere (unit) , acoustic wave , reflection (computer programming) , chromosphere , excitation , optics , interferometry , resonance (particle physics) , computational physics , acoustics , spectral line , atomic physics , astronomy , meteorology , quantum mechanics , computer science , programming language
High‐frequency p‐mode intensity data, obtained from the South Pole in 1987, 1988, 1990 and 1994, show a sharp variation in the phase‐shift function and in the frequency spacings near 5.5 mHz. Using a simple theoretical model, we demonstrate that this behaviour is caused by an acoustic resonance in the atmosphere between the excitation source and the upper reflection level. We discuss the diagnostic properties of this resonance, which is sensitive to the acoustic reflectivity of the solar atmosphere and to the location and parity of the excitation source. When applied to the solar data, our model indicates that the average acoustic reflectivity increases with increasing solar activity. The model also shows that the acoustic source has composite parity and is located within one pressure scaleheight of the base of the photosphere.