Sunspot photometry with phase diversity
I. Methods and global sunspot parameters
Kiepenheuer–Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, Germany e-mail: ali,wolfgang@kis.uni-freiburg.de
Corresponding author: A. Tritschler, ali@kis.uni-freiburg.de
Received:
8
May
2001
Accepted:
19
November
2001
The global brightness structure of a small sunspot is
investigated. Seeing and instrumental effects are
compensated by application of the phase-diversity
technique and a conventional deconvolution method.
We calculate brightness temperatures for the reconstructed data
in three simultaneously observed continuum bands of the solar spectrum
(402.1 nm, 569.5 nm, 709.1 nm).
The darkest umbral regions are on average
0.17
, 0.27 and
0.32 bright. The corresponding temperatures lie in the range
around 4790 K, 4600 K
and 4460 K. The spatially averaged penumbral
brightness amounts to 0.72,
0.81 and 0.85, which corresponds to
5910 K, 5750 K and 5640 K, respectively.
Although the spectral distribution of the umbral and penumbral
intensities is consistent with former measurements, the
derived values support the idea that
there exist a real difference in the
thermal properties between the umbrae of small and large sunspots.
Key words: Sun: sunspots / techniques: image processing
© ESO, 2002