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Modern Solar Facilities – Advanced Solar Science, 161–164 F. Kneer, K. G. Puschmann, A. D. Wittmann (eds.) c  Universitätsverlag Göttingen 2007 High-resolution CN spectroscopy of small-scale solar magnetic features V. V. Zakharov* , A. Gandorfer, and S. K. Solanki Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany * Email: zakharov@mps.mpg.de Abstract. High-resolution spectroscopic observations of small-scale magnetic elements in the solar photosphere were carried out in the spectral region 387.5–388.4 nm with the 1-m Swedish Solar Telescope (SST). This part of the spectrum covers not only the violet CN band-head, but also contains some lines of the CH molecule. The analysis of the line-core intensity contrasts of the CN and CH lines in bright points (BPs) yielded that on average the BPs appear brighter, thus providing a higher rms contrast, in the CN than in the CH lines in the same spectral band. 1 Observations Figure 1. Active region NOAA0753 observed near μ=0.95. The left panel (a) shows a high resolution red ”continuum” image (at λ =705.7 nm) restored with MFBD. The right panel (b) represents an example of a slit-jaw image taken in the violet CN band. The spectroscopic dataset presented here was collected with the TRIPPEL (TRI-Port Polarimetric Echelle-Littrow) spectrograph (Kiselman et al. 2007) installed at the SST. It was used simultaneously with the tip-tilt and the adaptive optics (AO) system and has a slit width of 25 μm, which corresponds to about 0.11 arcsec in the image plane. We have used a 162 V. V. Zakharov et al.: CN spectroscopy of bright points narrow-band interference filter (CWL=387.9 nm, FWHM=0.7 nm with 60 % peak transmission ) in front of the CCD camera as an order sorter. The light reflected by the slit box was used to obtain slit-jaw images in the violet CN band simultaneously with the spectra (e.g. Fig. 1 - right). The exposure time for spectra and slit-jaw images was 1.5 s. 10% of the total incoming sunlight were separated by a 90/10 grey beamsplitter in the light path before the spectrograph in order to obtain high resolution images in a red ”continuum” window using a narrow-band interference filter centered at 705.7 nm with a FWHM of 0.7 nm. These images, collected with exposure times of 10 ms, are uncorrelated in time with the spectroscopic dataset and are processed by the Multi Frame Blind Deconvolution (MFBD) routine (Löfdahl 2002), thus providing almost diffraction limited quality (e.g. Fig. 1 - left). All employed CCD cameras were Kodak Megaplus 1.6, 10 bit with 1536×1024 pixels of 9 μm each. We have observed on 14 April 2005 an active region NOAA0753 located near μ =0.95. Strong seeing variations and rotation of the FOV allowed us only to record few individual slit spectra, rather than full scans over some solar area. The analysed spectroscopic data were estimated to have 0.3 arcsec spatial resolution and a resolving power of 130 000. 2 Results Figure 2. Example of the observed CN spectrum of a BP (grey line) near μ=0.95 and of the quiet Sun (black line). The filter curve (dashed line) as obtained in the data reduction is also shown. In Fig. 2 a sample of observed CN spectra is shown. There are individual CH lines among the forest of CN lines in the observed wavelength band. In a BP (grey line) the spectrum shows a considerably reduced absorption in spectral lines of CN and CH as compared to that in a quiet Sun area. We have defined the contrast of intensity Iλ as Cλ = Iλ/ qs −1, where qs means the intensity averaged over a quiet Sun area in the immediate vicinity of the observed active region. In the present analysis we measured: • the line-core intensities ICH of a CH line at 387.72 nm and ICN of a CN line at 387.96 nm (marked in Fig. 2), V. V. Zakharov et al.: CN spectroscopy of bright points 163 Figure 3. Spectroscopic data observed in the active region NOAA0753 at μ=0.95 on 14 April 2005 at 14:56 (UT) : a) High-resolution red ”continuum” image; b) slit-jaw image; c) integrated and continuum intensity contrasts C (Iint) - black, C (Icont) - grey; d) line-core intensity contrasts C (ICN) - black, C (ICH) - grey; e) Bright Point Index; f) velocity measurements vCN in...

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