LESIA - Observatoire de Paris

Helioseismic requirements for a better representation of overshoot at the base of the convective envelope in the Sun and solar-type stars

Thursday 3 February 2011, by Mario Monteiro (Director Centro de Astrofisica, Universidade do Porto, Portugal)

Tuesday 15 February 2011 à 11h00 , Lieu : Salle de conférence du bât. 17

The stratification near the base of the Sun’s convective envelope is governed by processes of convective overshooting and element diffusion, and the region is widely believed to play a key role in the solar dynamo. The stratification in that region gives rise to a characteristic signal in the frequencies of solar p modes, which has been used to determine the depth of the solar convection zone and to investigate the extent of convective overshoot.
Previous helioseismic investigations have shown that the Sun’s spherically symmetric stratification in this region is smoother than that in a standard solar model without overshooting, and have ruled out simple models incorporating overshooting, which extend the region of adiabatic stratification and have a more-or-less abrupt transition to subadiabatic stratification at the edge of the overshoot region.
In this talk we discuss the constraints from Helioseismology, reported in http://xxx.lanl.gov/abs/1102.0235, through a detailed comparison with the Sun of physically motivated models which have a smooth transition in stratification bridging the region from the lower convection zone to the radiative interior beneath. We find that such a model is in better agreement with the helioseismic data than a standard solar model.
The seismic method developed to produce this analysis is discussed as well as the implications that such a result may have for the interpretation of seismic data of other solar-type stars.