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Acoustic oscillations in a field-free cavity under solar small-scale bipolar magnetic canopy

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Author(s): D. Kuridze | T. V. Zaqarashvili | B. M. Shergelashvili | S. Poedts

Journal: Annales Geophysicae
ISSN 0992-7689

Volume: 26;
Issue: 10;
Start page: 2983;
Date: 2008;
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ABSTRACT
Observations show the increase of high-frequency wave power near magnetic network cores and active regions in the solar lower atmosphere. This phenomenon can be explained by the interaction of acoustic waves with a magnetic field. We consider small-scale, bipolar, magnetic field canopy structure near the network cores and active regions overlying field-free cylindrical cavities of the photosphere. Solving the plasma equations we get the analytical dispersion relation of acoustic oscillations in the field-free cavity area. We found that the m=1 mode, where m is azimuthal wave number, cannot be trapped under the canopy due to energy leakage upwards. However, higher (m≥2) harmonics can be easily trapped leading to the observed acoustic power halos under the canopy.
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Tangokurs Rapperswil-Jona