Observations of Umbral Flashes
Abstract
We present observations of oscillations in the chromosphere of the umbra of sunspots. The observations were obtained with the Swedish Vacuum Solar Telescope (SVST) and the Dutch Open Telescope (DOT) on La Palma, comprising spectrograms and filtergrams in the Ca II H line. The sawtooth pattern in the spectroscopic time evolution of the Ca II H core is shown as well as evidence for a connection between umbral flashes and running penumbral waves from image sequences. Running waves, coherent over a large fraction of the penumbra, seem to be excited by flashes that occur close to the umbra-penumbral boundary. Comparing the intensity oscillations in the Ca II H line with TRACE observations in the 1600 Å passband, we find a phase difference of approximately 25 ° with 1600 Å leading the Ca II H intensity oscillation which we attribute to complex dynamical behaviour.
- Publication:
-
The Future of Cool-Star Astrophysics: 12th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun
- Pub Date:
- October 2003
- Bibcode:
- 2003csss...12..607R
- Keywords:
-
- Sun;
- Sunspots;
- Oscillations;
- SVST;
- DOT;
- TRACE