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Issue A&A Volume 374, Number 3, August II 2001 Page(s) L21 - L24 Section Letters DOI 10.1051/0004-6361:20010872

A&A 374, L21-L24 (2001)
DOI: 10.1051/0004-6361:20010872

The size of penumbral fine structure

P. Sütterlin

Sterrenkundig Instituut Utrecht, Postbus 80 000, 3507 TA Utrecht, The Netherlands

(Received 21 May 2001 / Accepted 19 June 2001 )

Abstract
I present power spectra of penumbral and granular intensity variations from a speckle-restored G-band image sequence of sunspot NOAA 9407 taken on April 1, 2001 with the Dutch Open Telescope on La Palma. I compare spatial power spectra of the sunspot penumbra with spatial power spectra from granulation with and without filigree. Relative to the granular power distribution, the penumbral power spectrum is enhanced over a wide range in spatial frequency peaking at 035. For smaller scales, the penumbral power distribution closely resembles that of the granular intensity variations. In contrast, the power spectrum of granulation with filigree exhibits increased power down to the resolution limit of 022, indicating the presence of unresolved magnetic elements.

Key words: Sun: magnetic fields -- sunspots

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© ESO 2001

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