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In the same way that seismologists study the interior of the earth from thewaves generated by earthquakes, heliosismology is the science that isinterested in the study of oscillatory waves inside the Sun. Temperature,chemical composition, rotational velocities at different depths are all factorsthat influence the oscillation frequencies of the waves trapped inside the Sun.The observation and measurement of the frequencies (or velocities) ofoscillations of the principal modes on the surface of the Sun allow us to studythe internal properties of the star. In our study, we use a local helioseismicmethod, called "Time-Distance"; the latter, after appropriate treatment(remapping, tracking, and filtering) of the data, which carried out from theGONG (Global Oscillation Network Group) observation network, allows us todeduce, by correlation of the observed signals, the relationship between thetime of the wave path and its crossed distance (hence the name of the method)between different points on the surface as a function of the different solarsub-surface parameters, via the dispersion relation. Once the travel times havebeen established by approximation of the correlation function by a Gaussianwave packet and based on the Fermat principle dealing with acoustic waves, wefind the relationship between these times and the internal parameters of thecrossed medium. Two models are considered in this study. The first does notinclude the effects of the magnetic field and takes into account the flowvelocity and the sound speed. The second, on the other hand, includes themagnetic effects, by means of the Alfven velocity (magnetic field perturbationvelocity), in addition to the parameters mentioned above. The last part of thispaper was devoted to the inversion of the obtained times, which allows us to goback to the solar internal parameters.

Etude et mise en oeuvre des techniques Temps-Distance en Heliosismologie