EDP Sciences
Free access
Volume 394, Number 3, November II 2002
Page(s) 1069 - 1076
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20021196

A&A 394, 1069-1076 (2002)
DOI: 10.1051/0004-6361:20021196

2D-spectroscopic observations of $\vec G$-band bright structures in the solar photosphere

K. Langhans, W. Schmidt and A. Tritschler

Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, Germany

(Received 10 June 2002 / Accepted 7 August 2002 )

We took two-dimensional spectra with the filter spectrometer TESOS at the German Vacuum Tower Telescope, Tenerife, of an absorption line of the CH molecule and a Fe II-line in the G-band at 430.3 nm. We observed a region, close to disk center of the Sun, that showed a lot of structures with enhanced G-band intensity (up to 1.3 times the mean intensity of normal granulation). Our spectroscopic investigation of these structures suggests two classes which differ in their spectroscopic signature: (a) Bright structures caused by significant (up to 40%) weakening of absorption lines of the CH molecule; (b) bright structures only caused by an enhanced continuum intensity. In order to distinguish between those two classes we introduce a Bright Point Index (BPI) defined by the ratio of the normalized line depressions of the Fe II and the CH-line. The bright structures caused by weakening of the CH-lines have high BPI values and are accompanied by downflows. The remaining G-band bright structures have low BPI and are related to granules.

Key words: Sun: photosphere

Offprint request: K. Langhans, kai@kis.uni-freiburg.de

© ESO 2002