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A&A 443, L7-L10 (2005)
DOI: 10.1051/0004-6361:200500179
Letter
Multi-line spectroscopy of dark-cored penumbral filaments
L. R. Bellot Rubio1, K. Langhans2 and R. Schlichenmaier31 Instituto de Astrofísica de Andalucía (CSIC), Apdo 3004, 18080 Granada, Spain
e-mail: lbellot@iaa.es
2 Institute for Solar Physics, Royal Swedish Academy of Sciences, Alba Nova University Center, 10691 Stockholm, Sweden
3 Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, Germany
(Received 1 July 2005 / Accepted 3 September 2005 )
Abstract
Dark-cored filaments could be the basic building blocks of
sunspot penumbrae. Yet, their nature and physical conditions are
unknown. In an attempt to improve this situation, we present the first
high-resolution spectra of dark-cored penumbral filaments. Several
such filaments were observed near the umbra/penumbra boundary of a
sunspot located at heliocentric angles of 5° and 20°.
Our data reveal (a) significantly larger Doppler shifts in the dark
cores as compared to their lateral brightenings; (b) Doppler shifts
that increase with depth in the photosphere, up to 1.5 km s-1;
and (c) Doppler shifts that increase with increasing heliocentric
distance. The Doppler velocities measured in the dark cores are almost
certainly produced by upflows. In addition, dark-cored penumbral
filaments exhibit weaker fields than their surroundings (by
100-300 G). These results provide new constraints for models of
dark-cored penumbral filaments.
Key words: Sunspots -- Sun: photosphere -- line: profiles
© ESO 2005