POSTER PAPER 1.05
Observations of Umbral Flashes
L.H.M. Rouppe van der Voort, J.M. Krijger
Institute: Research Station for Astrophysics of the Royal
Swedish Academy of Sciences
Institute:S terrekundig Instituut, Utrecht University
Contact Email: rouppe@astro.su.se
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 A passband, we find a phase difference of approximately
25 degrees with 1600 A leading the Ca II H
intensity oscillation which we attribute to complex dynamical
behaviour.
Index Keywords: Sun ; Sunspots ; Oscillations ; SVST ; DOT ; TRACE
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Manuscript submitted: 2001-Sep-6
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.