Seismology of the Solar Envelope - the Base of the Convective Zone as Seen in the Phase Shift of Acoustic Waves

Details Seismology of the Solar Envelope - the Base of the Convective Zone as Seen in the Phase Shift of Acoustic Waves Seismology of the Solar Envelope - the Base of the Convective Zone as Seen in the Phase Shift of Acoustic Waves

Jun 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994mnras.268..880r&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Vol. 268, NO. 4/JUN15, P. 880, 1994

Astronomy and Astrophysics

Astronomy

61

Waves - Sun: Interior - Sun: Oscillations - Stars: Oscillations

Scientific paper

At the base of the convective zone, discontinuities in the derivatives of the sound speed produce a phase shift in acoustic waves. This phase shift, α0(ν), is inferred by matching the measured solar p-modes to a second-order asymptotic description, the contribution from the surface layers and the second helium ionization zone being subtracted using modes with turning points well inside the convective zone. The resulting phase shift varies quasi-periodically with frequency with a period ≍220 μHz, and has an amplitude ≍8(±4) × 10-4 at a frequency of 3000 μHz. The phase shift α0(ν) is also calculated using the same technique for two solar models, one with no convective penetration and one with penetration extending for 1 per cent of the solar mass.
We estimate the predicted phase shift for models of the convective zone, including possible convective penetration modelled by extending the zone a distance ɛHp below the classical boundary; α(ν) has a quasi-periodic contribution with period ≍1/(2τβ), where τβ = ∫ dr/c is the acoustic depth of the base of the zone, and with amplitude [ADS note: formula could not be rendered in ASCII.] where f(ɛ) and h(ɛ) are functions of ɛ which also depend on the variation of opacity with temperature and density. For ν = 3000 μHz, and typical values at the base of the convective zone, AV = 5& × 10-4 for ɛ = 0, decreases slightly for small ɛ and then increases to 1 × 10-3 for ɛ = 0.25, and to 1.7 × 10-3 for ɛ = 0.5.
The currently available data are consistent with an overshooting parameter 0≤ɛ≤0.25.

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