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

• Main Authors: D. Kuridze, T. V. Zaqarashvili, B. M. Shergelashvili, S. Poedts
• Format: Article
• Language: English
• Published: Copernicus Publications 2008-10-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/26/2983/2008/angeo-26-2983-2008.pdf

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 <I>m</I>=1 mode, where <I>m</I> is azimuthal wave number, cannot be trapped under the canopy due to energy leakage upwards. However, higher (<I>m</I>&ge;2) harmonics can be easily trapped leading to the observed acoustic power halos under the canopy.