6.4 p-mode line profiles

The interaction between the oscillations, convection and radiation is also responsible for the asymmetry of the mode’s spectra and the reversal of asymmetry between velocity and intensity. There is disagreement as to which is the dominant mechanism producing the asymmetry and its reversal. The Green’s function for the response to excitation has an asymmetry that depends on the depth of the source. The superposition of correlated noise to the oscillation signal will produce a reversal of asymmetry between velocity and intensity (Nigam et al., 1998Kumar and Basu, 1999). Such a reversal can also be produced by radiative transfer effects (Georgobiani et al., 2003). In addition, the vertical oscillation motions move the height of the steep background temperature gradient in the low photosphere up and down, which tends to cancel the effect caused by oscillation induced opacity fluctuations (Straus et al., 2006). These effects dominate over the intrinsic wave properties in controlling the phase relation between temperature and velocity.

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