Seismic diagnostics of the equation of stateand element abundances in the solar envelope

S. V. Vorontsov1,2, V. A. Baturin3, S. V. Ayukov3, V. K. Gryaznov4

1Astronomy Unit, Queen Mary, University of London2Institute of Physics of the Earth, Moscow3Sternberg State Astronomical Institute of Lomonosov Moscow State University4Institute of Problems of Chemical Physics RAS, Chernogolovka, Russia

Calibration with p-mode frequencies (MDI 15 years)

Calibration with p-mode frequencies (MDI 1 year)

Calibration with p-mode frequencies (MDI 1 year)

Inversion for the adiabatic exponent, SAHA-S3

Inversion for the adiabatic exponent, SAHA-S5

Inversion for the adiabatic exponent, SAHA-S5 mixture OPAL

Inversion for the adiabatic exponent, OPAL-2005

Effects of heavy elements in the adiabatic exponent

Group velocity of surface waves

First-order asymtotic description:

Inversion with model SResidualsBefore and after inversion

Inversion for the adiabatic exponent Residuals before the inversion

Calibration with group velocities (MDI 1year)

Superadiabatic temperature gradient

Conclusions

SAHA-S equation of state allows to achieve better agreement with seismic data, when compared with OPAL equation of state

All our results support the downward revision of solar metallicity.

Further work

Seismic measurement of C- and O abundances.

This will require reduction of systematic errors in frequencymeasurements, with possible extension of the degree range

p-mode frequency data sets

SOHO MDI ‘Medium-l’ program

(1) 15-years frequency averaging

(2) 5-yrs averaging, high activity

(3) First year, low solar activity

(4) as (3) but with new measurementdescribed in Vorontsov, Jefferies, Giebink,Schou, 2009, Toward Eliminating SystematicErrors in Intermediate-Degree p-ModeMeasurements, ASP Conf. Series 416, 301

Envelope calibration:blue-data set 1 (15yrs), red-data set 2 (5yr high activity)

Envelope calibration:blue-data set 3, red-data set 4 (1yr low activity)

Blue: mass coordinate:data set 4 (1yr low activity)

Inversiondata set 1 (15 years)

Inversion: SAHA-S3data set 1 (15 years)

Inversion: Model Sdata set 1 (15 years)

Conclusions

• Despite of systematic errors, and limitations in degree range, p-mode dataallows to compare the performance of modern versions of the equation of state, and allows simultaneous measurement of solar Y and Z values

• The best agreement with seismic data is provided by the most recentSAHA-S3 equation of state

• All our results support the downward revision of solar Z value.