Granulation in active regions as compared to quiet regions

Hirzberger, J.; Bonet, J. A.; Vázquez, M.; Hanslmeier, A.; Sobotka, M.
Bibliographical reference

AG Abstract Services, vol. 15. Abstracts of Contributed Talks and Posters presented at the Annual Scientific Meeting of the Astronomische Gesellschaft, in Goettingen, 20-25 September 1999.

Advertised on:
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1999
Number of authors
5
IAC number of authors
1
Citations
0
Refereed citations
0
Description
A comparative study of the statistical properties of granulation in active and quiet regions is performed. The analysis is based on a high-resolution time series of simultaneous white light (lambda5425 Å) and G-band (lambda 4308 Å) images obtained at the Swedish Vacuum Solar Telescope, La Palma, Canary Islands. The G-band images have been used to discern quiet and active regions in the field of view, whereas the white-light images were taken to analyze the photometry, size and time evolution of granules in regions of different magnetic activity. Power spectra confirm that the granular size decreases with increasing G-band brightness. Granules with diameters below 0''.8 are systematically brighter in the abnormal granulation than in quiet regions. These small and bright elements are embedded in a diffuse background of approximately mean photospheric brightness covering all the fields of abnormal granulation. The granular lifetime decreases with increasing G-band brighness. The conclusions about the behaviour of the granulation have been decontaminated of the influence of magnetic elements (the so-called Bright Points), that have been separated using criteria of size (d < 0''.5) and lifetime (T > 6 min). A significant fraction of them are concentrated in regio ns of high G-band activity, an emerging flux region, and the rest are mainly aligned outlining a cellular pattern (the magnetic network formed by supergranular motions).