UVSP/SMM observations of transition region oscillations in sunspots
Abstract
Using Ultraviolet Spectrometer and Polarimeter data obtained in emission lines formed at temperatures of 70,000 K to 130,000 K, transition region oscillations in sunspots have been observed. The frequency of these oscillations lies in the range 5.8 mHz to 7.8 mHz. Their regular appearance in line-of-sight velocity and their frequent occurrence in intensity in phase with maximum blue shift leads to the interpretation of the oscillations as upward-propagating acoustic waves. The presence in two of the C IV wavelength 1548.19 time series of a phase-shifted oscillation in the line width may be caused by the presence of unidentified blends in the line wings. The energy flux carried by the umbral acoustic waves is less than 2000 erg/sq cm/s, some seven orders of magnitude smaller than the missing radiative flux of sunspots.
- Publication:
-
The Physics of Sunspots
- Pub Date:
- 1981
- Bibcode:
- 1981phss.conf..319G
- Keywords:
-
- Solar Oscillations;
- Sunspots;
- Time Series Analysis;
- Ultraviolet Astronomy;
- Fast Fourier Transformations;
- Line Spectra;
- Power Spectra;
- Ultraviolet Spectroscopy;
- Solar Physics