1112.4790 (Bradley W. Hindman)
Bradley W. Hindman
In a power spectrum of the Sun's acoustic waves, the p modes have distinctly
skewed frequency profiles. Furthermore, the asymmetry is observed to have the
opposite sign in power spectra made from line-of-sight velocity and continuum
intensity. The asymmetry and its reversal in sign has previously been explained
using a combination of mechanisms that involve the acoustic source. A localized
acoustic source within an acoustic cavity naturally generates asymmetric
profiles through wave interference; however, the sign of the asymmetry due to
this mechanism is identical for all observables. The reversal of the asymmetry
between velocity and intensity observations has been attributed to the
visibility of the source itself (i.e., "correlated noise"). In this paper, I
will show that asymmetry generated by a localized source can be interpreted as
either a wave interference effect in physical space, or a mode interference
effect in spectral space. I advocate a new mode-fitting procedure based on this
new interpretation, whereby the complex phases of all the modes determine the
mode asymmetries. Further, I suggest that information about the acoustic source
function is encapsulated in the amplitude of each mode, and present a scheme by
which the source function can be obtained from measured mode amplitudes by
standard helioseismic inversion techniques.
View original:
http://arxiv.org/abs/1112.4790
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