Directional time–distance probing of model sunspot atmospheres

Moradi, H, Cally, PS, Przybylski, D and Shelyag, Sergiy 2015, Directional time–distance probing of model sunspot atmospheres, Monthly notices of the Royal Astronomical Society, vol. 449, no. 3, pp. 3074-3081, doi: 10.1093/mnras/stv506.

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Title Directional time–distance probing of model sunspot atmospheres
Author(s) Moradi, H
Cally, PS
Przybylski, D
Shelyag, SergiyORCID iD for Shelyag, Sergiy
Journal name Monthly notices of the Royal Astronomical Society
Volume number 449
Issue number 3
Start page 3074
End page 3081
Total pages 8
Publisher Oxford University Press
Place of publication Oxford, Eng.
Publication date 2015-05-21
ISSN 0035-8711
Keyword(s) Science & Technology
Physical Sciences
Astronomy & Astrophysics
Sun: helioseismology
Sun: oscillations
Summary A crucial feature not widely accounted for in local helioseismology is that surface magnetic regions actually open a window from the interior into the solar atmosphere, and that the seismic waves leak through this window, reflect high in the atmosphere, and then re-enter the interior to rejoin the seismic wave field normally confined there. In a series of recent numerical studies using translation invariant atmospheres, we utilized a ‘directional time–distance helioseismology’ measurement scheme to study the implications of the returning fast and Alfvén waves higher up in the solar atmosphere on the seismology at the photosphere (Cally & Moradi 2013; Moradi & Cally 2014). In this study, we extend our directional time–distance analysis to more realistic sunspot-like atmospheres to better understand the direct effects of the magnetic field on helioseismic travel-time measurements in sunspots. In line with our previous findings, we uncover a distinct frequency-dependent directional behaviour in the travel-time measurements, consistent with the signatures of magnetohydrodynamic mode conversion. We found this to be the case regardless of the sunspot field strength or depth of its Wilson depression. We also isolated and analysed the direct contribution from purely thermal perturbations to the measured travel times, finding that waves propagating in the umbra are much more sensitive to the underlying thermal effects of the sunspot.
Language eng
DOI 10.1093/mnras/stv506
Field of Research 0201 Astronomical And Space Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2015, The Authors
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