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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 26, issue 10
Ann. Geophys., 26, 2983–2989, 2008
https://doi.org/10.5194/angeo-26-2983-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: SOHO 20 – Transient events on the Sun and in the...

Ann. Geophys., 26, 2983–2989, 2008
https://doi.org/10.5194/angeo-26-2983-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

  15 Oct 2008

15 Oct 2008

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

D. Kuridze1, T. V. Zaqarashvili1, B. M. Shergelashvili1,2, and S. Poedts3 D. Kuridze et al.
  • 1Georgian National Astrophysical Observatory (Abastumani Astrophysical Observatory), Al. Kazbegi ave. 2a, 0160 Tbilisi, Georgia
  • 2Institute for Theoretical Physics, K.U. Leuven, Celestijnenlaan 200 D, 3001, Leuven, Belgium
  • 3Center for Plasma Astrophysics, K.U.Leuven, 200 B, 3001, Leuven, Belgium

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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