Oscillation of the magnetic field in an active region.
Abstract
The solar vacuum telescope VTT at Tenerife has been used to obtain high-resolution two-dimensional spectro-polarimetric observations of oscillations in the photospheric layers of sunspots. The spectra of velocity oscillations show the known features of closely packed power peaks in bands of periods around 3 min (strengthened) and 5 min (weakened with respect to the quiet Sun). In the same frequency bands the VTT data show significant oscillations of the magnetic field strength as well, which could not be attributed to disturbing influences. Maximum power of both velocity and magnetic oscillations and a strong correlation between them, in the 3-min band in particular, is found to occur in those parts of the umbra where the magnetic lines of force are parallel to the line-of-sight. The oscillations are characterized by a marked spatial fine structure and a non-stationary behaviour.
- Publication:
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JOSO Annu. Rep., 1997
- Pub Date:
- 1998
- Bibcode:
- 1998joso.proc...79H
- Keywords:
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- Solar Active Regions: Solar Magnetic Fields;
- Solar Magnetic Fields: Sunspots;
- Solar Magnetic Fields: Oscillations