Issue |
A&A
Volume 381, Number 1, JanuaryI 2002
|
|
---|---|---|
Page(s) | 279 - 289 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20011419 | |
Published online | 15 January 2002 |
8542 Å sunspot oscillations observed with
THEMIS*
1
Observatoire de Paris, Section de Meudon, DASOP, 92195 Meudon Principal Cedex, France e-mail: Kostas.Tziotziou@obspm.fr, e-mail: Pierre.Mein@obspm.fr
2
National Observatory of Athens, Institute for Space Applications and Remote Sensing, 15236 Palea Penteli, Greece e-mail: georgia@space.noa.gr
Corresponding author: K. Tziotziou, Kostas.Tziotziou@obspm.fr
Received:
25
April
2001
Accepted:
7
September
2001
Oscillations in the umbra and the penumbra of an isolated
sunspot located near the solar disk centre were investigated.
The observations were obtained with the Multichannel Subtractive Double
Pass (MSDP) spectrograph operating in the 8542 Å line and installed
at the focus of THEMIS (Tenerife). From the MSDP data, two-dimensional
intensity and Doppler shift images were computed at different
wavelengths within the line.
Intensity and Doppler shift oscillations in the umbra and the
penumbra of the sunspot showing up as umbral flashes and penumbral
waves were analyzed using a 23 min time series with a cadence of 46 s.
The
umbral flash intensity profile shows an emission core
in its blue wing. We investigate the relation between umbral flashes
and running penumbral waves by a power spectrum analysis which
shows a 6 mHz frequency for the standing umbral oscillations
(flashes) which are observed only on the upper half part of the
umbra. The running penumbral waves propagate with an average phase
velocity of 16 and their frequency is constant in the penumbra
and equal to 3 mHz. Although the time slice images suggest that umbral flashes
and running penumbral waves are probably due to the same resonator,
the power analysis shows no direct relationship between the two phenomena.
Key words: Sun: chromosphere / Sun: oscillations / Sun: sunspots
© ESO, 2002
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