HELIOSEISMIC MEASUREMENT OF THE EXTENT OF OVERSHOOT BELOW THE SOLAR CONVECTION ZONE

The discontinuity in the derivatives of the sound speed at the base of the overshoot layer below the solar convection zone introduces a characteristic oscillatory component in the frequencies of solar p-modes as a function of the radial order n. The amplitude of this oscillatory part is calibrated as a function of the extent of overshoot using a sequence of solar models constructed with varying extent of overshoot. Using this calibration, an attempt is made to measure the extent of overshoot below the solar convection zone using the available frequencies of the p-modes. It is found that the observed frequencies are consistent with a solar model without overshoot. Further, taking account of the errors in observations, it is possible to put a 2sigma upper limit of 0.1 H(p) on the extent of overshoot.