Issue |
A&A
Volume 375, Number 2, August IV 2001
|
|
---|---|---|
Page(s) | 617 - 628 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20010887 | |
Published online | 15 August 2001 |
Oscillations and running waves observed in sunspots*
III. Multilayer study
1
Electronics Laboratory, University of Patras, Patras 26110, Greece e-mail: echris@physics.upatras.gr
2
Solar Astronomy, California Institute of Technology, Pasadena, CA 91125, USA e-mail: ageorg@caltech.edu
3
Institut d'Astrophysique de Paris, CNRS, 98 bis boulevard Arago, 75014 Paris, France e-mail: koutchmy@iap.fr
Corresponding author: A. A. Georgakilas, ageorg@CALTECH.edu
Received:
12
April
2001
Accepted:
28
May
2001
We continue our study of waves and oscillations observed in sunspots
using an improved method for enhancing the waves, giving the opportunity to
identify them and determine their properties in far Hα wings.
We found that the running penumbral waves are observable at least up to the
formation height of the H Å line, but not in the
H
Å or the
Å. We found a time lag between
the waves in the blue and the red wing of the Hα line corresponding to a phase
shift of 180°, that indicates a pure Doppler shift of the line. There is a
lag in the propagation of the waves seen at Hα center and at Hα wings.
Also there is a lag in the variation of the umbral oscillations as they are
observed from lower to higher atmospheric layers. The correlation between umbral
oscillations at various atmospheric heights and running penumbral waves strongly
indicates that the latter are excited by photospheric umbral oscillations and not
the chromospheric ones. We found a new category of photospheric waves that originate
at approximately 0.7 of the distance between the umbra and the penumbra boundary and
propagate beyond the outer penumbra boundary with a velocity of the order of
3-4 km s-1. Further, we found 3 min penumbral oscillations apparent in the
inner penumbra at lower chromospheric layers (far Hα wings).
Key words: Sun: sunspots / Sun: oscillations
© ESO, 2001
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