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Helioseismology of Sunspots: An Extended Analysis of AR 9787

Auteur

Moradi Hamed

Institution

Max Planck Institute for Solar System Research

Theme

Local helioseismology
Auteur(s) supplémentaire(s)Baldner, C.; Birch, A. C.; Braun, D.; Cameron, R.; Duvall, T. L., Jr.; Gizon, L.; Haber, D.; Hanasoge, S.; Jackiewicz, J.; Khomenko, E.; Komm, R.; Rajaguru, P.; Rempel, M.; Roth, M.; Schlichenmaier, R
Institution(s) supplémentaire(s)Schunker, H.; Spruit, H.; Strassmeier, K.; Thompson, M. J.; Zharkov, S.

Abstract

In general, there are two main conjectures for the structure of the subsurface magnetic configuration of a sunspot: the monolithic model and the jellyfish/cluster/spaghetti model. Determining the parameters of these flux tubes, that is, their typical size, field strength, etc., will help reveal details of the operation of the solar dynamo and how magnetic field is transported up through the convection zone. Helioseismology may have the potential to distinguish between these models, and to date, there have been many conclusions drawn about sunspot and active region structure from local helioseismology. But despite the long history of work on this topic, there is no general agreement on the subsurface structure of active regions. In this work, we provide a follow-up to the detailed helioseismic study of the active region AR 9787. This sunspot was observed during the period 20--28 January 2002 by the SOHO/MDI instrument. Various helioseismic diagnostic tools are used to investigate the possible causes of the inconsistencies between the methods. We find that most inferences regarding the subsurface structure of AR 9787 point to the conclusion that this sunspot is associated with a shallow positive wave-speed perturbation and that it is surrounded by a horizontal outflow. In addition, we demonstrate that direct simulations of wave propagation through a model sunspot are capable of reproducing many features of the helioseismic measurements.
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