Acoustic oscillations in a field-free cavity under solar small-scale bipolar magnetic canopy
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...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2008-10-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/26/2983/2008/angeo-26-2983-2008.pdf |
| Summary: | 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>≥2) harmonics can be
easily trapped leading to the observed acoustic power halos under
the canopy. |
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| ISSN: | 0992-7689 1432-0576 |