Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Full Refereed Journal Article (PDF/Postscript)
· Full Refereed Scanned Article (GIF)
· References in the article
· Citations to the Article (63) (Citation History)
· Refereed Citations to the Article
· Associated Articles
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
Oscillations and running waves observed in sunspots
Authors:
Christopoulou, E. B.; Georgakilas, A. A.; Koutchmy, S.
Affiliation:
AA(Thessalias 13, 13231 Petroupoli, Athens, Greece ), AB(Thessalias 13, 13231 Petroupoli, Athens, Greece ), AC(Institut d'Astrophysique de Paris, CNRS, 98 bis boulevard Arago, 75014 Paris, France )
Publication:
Astronomy and Astrophysics, v.354, p.305-314 (2000) (A&A Homepage)
Publication Date:
02/2000
Origin:
A&A
Astronomy Keywords:
SUN: SUNSPOTS, SUN: OSCILLATIONS
Bibliographic Code:
2000A&A...354..305C

Abstract

In order to study umbral oscillations, running penumbral waves and the relationship between them, we analyzed CCD, high resolution, sunspot observations obtained at center and the wings of the Hα line and the Fe I 5576 Ä line. The UBF filter was used in order to produce high cadence sequences of filtergrams. Images were processed to remove the sharp intensity gradient between the umbra and the penumbra. They show the waves to start out around umbral oscillating elements and to propagate outwards forming concentric cycles around the elements. The waves appear to propagate beyond the outer edge of the photospheric penumbra, in the superpenumbra, where they dilute. Comparing images in 9 wavelengths along the Hα profile we found out that the waves are definitely better observed near the Hα center and near the blue wing -0.35 Ä. This indicates a possible vertical upward mass motion in the oscillating penumbral structure and that the oscillation is not symmetric about zero. We found different oscillating modes. Standing umbral oscillations are dominant in the umbra and inner penumbra; their frequency is around 6.5 mHz. Similar oscillations are observed in the penumbra - superpenumbra boundary but with considerably lower frequency (2 mHz). Oscillations are absent or have reduced magnitude in the central part of the penumbra. Penumbral waves are running waves propagating with a constant phase velocity around 13 km s-1; their frequency is remaining constant over the whole penumbra, in the band of 3 mHz. We produced ``time slice images" which show, that there is not a clear relationship between umbral oscillations and running penumbral waves.

Associated Articles

Part  1     Part  2     Part  3    

Printing Options

Print whole paper
Print Page(s) through

Return 600 dpi PDF to Acrobat/Browser. Different resolutions (200 or 600 dpi), formats (Postscript, PDF, etc), page sizes (US Letter, European A4, etc), and compression (gzip,compress,none) can be set through the Printing Preferences


More Article Retrieval Options

HELP for Article Retrieval
Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)

Find Similar Abstracts:

Use: Authors
Title
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints