Photospheric high-frequency acoustic power excess in sunspot umbra: signature of magneto-acoustic modes

Zharkov, Sergei, Shelyag, Sergiy, Fedun, Viktor, Erdélyi, Robert and Thompson, Michael John (2013) Photospheric high-frequency acoustic power excess in sunspot umbra: signature of magneto-acoustic modes. Annales Geophysicae, 31 (8). pp. 1357-1364. ISSN 1432-0576

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Official URL: http://dx.doi.org/10.5194/angeo-31-1357-2013

Abstract

We present observational evidence for the presence of MHD (magnetohydrodynamic) waves in the solar photosphere deduced from SOHO/MDI (Solar and Heliospheric Observatory/Michelson Doppler Imager) Dopplergram velocity observations. The magneto-acoustic perturbations are observed as acoustic power enhancement in the sunspot umbra at high-frequency bands in the velocity component perpendicular to the magnetic field. We use numerical modelling of wave propagation through localised non-uniform magnetic field concentration along with the same filtering procedure as applied to the observations to identify the observed waves. Guided by the results of the numerical simulations we classify the observed oscillations as magneto-acoustic waves excited by the trapped sub-photospheric acoustic waves. We consider the potential application of the presented method as a diagnostic tool for magnetohelioseismology.

Item Type: Article
Uncontrolled Keywords: magnetic fields, photosphere, chromosphere
Subjects: F300 Physics
F500 Astronomy
G100 Mathematics
Department: Faculties > Engineering and Environment > Mathematics and Information Sciences
Depositing User: Sergiy Shelyag
Date Deposited: 23 May 2016 09:54
Last Modified: 13 May 2017 13:32
URI: http://nrl.northumbria.ac.uk/id/eprint/26896

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