Dean-Yi Chou(Physics Department, National Tsing Hua University, Hsinchu, Taiwan)

The solar acoustic waves are modified by the interaction with sunspots. The interaction can be treated as a scattering problem: an incident wave propagating toward a sunspot is scattered by the sunspot into different modes. The absorption cross section and scattering cross section are two important parameters in the scattering problem. In this study, we use the wavefunction of the scattered wave, measured with a deconvolution method, to compute the absorption cross section σab and the scattering cross section σsc for the radial order n = 0 − 5 for two sunspots, NOAAs 11084 and 11092. In the computation of the cross sections, the random noise and dissipation in the measured acoustic power are corrected. For both σab and σsc, the value of NOAA 11092 is greater than that of NOAA 11084, but their overall n dependences are similar: decreasing with n. The ratio of σabs of two sunspots is approximately equal to the ratio of sunspot radii for all ns, while the ratio of σscs of two sunspots is greater than the ratio of sunspot radii and increases with n. This suggests that σab is approximately proportional to the sunspot radius, while the change of σsc with radius is faster than the linear increase.