Abstract Details
| Name: Jishnu Bhattacharya Affiliation: Tata Institute of Fundamental Research Conference ID: ASI2016_665 Title : Strategies in seismic inference of supergranular flows on the Sun Authors and Co-Authors : Shravan M. Hanasoge, Tata Institute of Fundamental Research Abstract Type : Poster Abstract Category : Sun and the Solar System Abstract : Observations of the Solar surface reveal the presence of flows spanning tens to hundreds of mega-meters, commonly referred to as supergranules. Inferring the sub-surface flow profile of supergranules from measurements of the surface and photospheric wavefield is an important challenge faced by helioseismology. Traditionally the inverse problem has been approached through linear kernels (Gizon et al., 2002; Dombroski et al., 2013); however it is believed that an iterative approach would perform better than single-step, linear inversions (Hanasoge, 2014). In this paper, we simulate `observed wavefield' starting from a specific 2-dimensional supergranule profile (Duvall et al., 2013), and use the SPARC code (Hanasoge et al., 2007) to update our model of the flow by iteratively reducing the travel-time misfit between the `observed wavefield' and the one predicted by our model. We investigate the impact of strategies such as spatio-temporal and spectral filtering on the accuracy and speed of convergence of the inversion. We show that the inversion proceeds through correcting surface layers before deeper layers, and that large-distance measurements or equivalently high-order p-modes are necessary to infer the profile of the flow beyond the depth of a mega-meter. We demonstrate that limited depth sensitivity leads to inaccurate estimation of velocity magnitudes, especially for vertical component of velocity. |