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Oscillations and running waves observed in sunspots. III. Multilayer study

Christopoulou, E. B. and Georgakilas, A. A. and Koutchmy, S. (2001) Oscillations and running waves observed in sunspots. III. Multilayer study. Astronomy & Astrophysics, 375 (2). pp. 617-628. ISSN 0004-6361. doi:10.1051/0004-6361:20010887.

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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 Hα ± 0.5 Å line, but not in the H Hα ± 0.75 Å or the FeI ± 0.12 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).

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Additional Information:© 2001 ESO. Article published by EDP Sciences. Received 12 April 2001; Accepted 28 May 2001; Published online 15 August 2001. Based on observations performed on the NSO/SPO Richard B. Dunn Solar Telescope (DST). We would like to thank Dr. R. N. Smartt, the T.A.C. of NSO/SP and the staff of the Sacramento Peak Observatory, especially the Observers team of the DST, for their warm hospitality and their help with the observations. Further, we would like to thank the referee (Dr. H. Wöhl) for his suggestions that helped improve the text. This work was partially supported by NSF grant ATM-9726147.
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Subject Keywords:Sun: sunspots - Sun: oscillations
Issue or Number:2
Record Number:CaltechAUTHORS:20180214-092417864
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Official Citation:Oscillations and running waves observed in sunspots - III. Multilayer study E. B. Christopoulou, A. A. Georgakilas and S. Koutchmy A&A, 375 2 (2001) 617-628. DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84827
Deposited By: Tony Diaz
Deposited On:14 Feb 2018 20:30
Last Modified:15 Nov 2021 20:23

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