SOHO CoRoT Kepler Picard SDO GONG

The Need for Physics-based Inversions of Sunspot Structure and Flows


Braun Douglas


NorthWest Research Assoc., CoRA DIvision


Local helioseismology
Auteur(s) supplémentaire(s)A. Birch, A. Crouch (1), M. Rempel (2)
Institution(s) supplémentaire(s)(1) NWRA/CoRA (2) NCAR/HAO


A NASA funded SDO Science Center project, begun in early 2009, has been tasked with understanding the physics responsible for the helioseismic signals in and around magnetic regions and developing new procedures which can be applied to data from the HMI instrument on SDO. Current controversy exists in the interpretation and modeling of travel-time measurements in sunspots. Unresolved issues include the dependence of the sign of both the inferred flows and wave speed on the type of filtering used, and the discrepancy between the relatively deep two-layer wave-speed models derived from standard time-distance methods and shallow, positive wave-speed models derived using forward models which include effects of mode conversion To make full use of the year-round, almost limb-to-limb, coverage provided by HMI, an efficient and reliable inversion method incorporating possible magnetic effects and the currently unexplained sensitivity to methodology is critical. Key components of the effort to understand and resolve these issues include numerical computations of wave propagation through model sunspots, including realistic MHD models developed at NCAR, as well as translationally invariant models developed at NWRA. This work is supported by the NASA SDO Science Center Program (contract NNH09CE41C).
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