MDI-VIRGO-GOLF proposal
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Title : Inversion of the solar core structure

1) Lead investigator: Provost Janine

2) Members of the collaboration:
Appourchaux, T., (ESA, CO-I VIRGO)
Berthomieu,  G., (Nice Observatory, CO-I VIRGO, A.S. GOLF)
Corbard,     T., (Nice Observatory)
Gonczi,      G., (Nice Observatory)
Kosovichev,  A., (Stanford, MDI CO-I)
Morel,       P., (Nice Observatory)
Provost,     J., (Nice Observatory, CO-I VIRGO, A.S. GOLF)
Toutain,     T., (Nice Observatory, CO-I VIRGO, A.S. GOLF)

3) Abstract: We propose a joint analysis of the MDI, VIRGO, GOLF data
which consists in combining their frequencies and inverting them to infer
the structure of the solar core


4) Description of the project
 It comes out from the inversion of the IPHIR+BBSO, BISON+BBSO and LOWL
frequencies that the structure of the solar core is still a controversial
issue.
 We would like to take advantage of the frequencies of the very low-degree
low-order p modes and possibly g modes that VIRGO and GOLF will provide
by combining them with the SOI frequencies to infer the structure of
the solar core.
 Low-degree mode frequencies will be obtained from the LOI and GOLF spectra
using a maximum likelihood fitting package already avalaible and tested on
IPHIR
data and real LOI data. The SOI frequencies will be obtained using the "peak
bagging" package developed by A. Kosovichev and S. Korzennik

The inversion will be performed using a regularized least square inversion code
of the p- and g-modes frequencies which is under developement in Nice.
This code approximates the functions to be inferred by piecewise polynomials
projected on B-splines of arbitrary order.

We are studying how we could take advantage of the properties of B-splines
mainly for improving the regularization procedure, and the description of rapid
variations of the solution. In particular, we will test the influence of the
form of the regularizing terms on the inversed structure and the influence of
the surface effects.

A wide range of solar models, provided by P. Morel with his code CESAM
of stellar evolution, will be used on that purpose.