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Modern Solar Facilities – Advanced Solar Science, 217–220 F. Kneer, K. G. Puschmann, A. D. Wittmann (eds.) c  Universitätsverlag Göttingen 2007 Temporal evolution of intensity, velocity and magnetic field of sunspots at high spatial resolution N. Bello González* , F. Kneer, and K. G. Puschmann Institut für Astrophysik, Göttingen, Germany * Email: nazaret@astro.physik.uni-goettingen.de Abstract. We present results of sunspot observations obtained in April 2006 with the new ’Göttingen’ Fabry-Perot spectrometer. Thanks to the large field of view (77 × 58 ) of the new optical setup it has been possible to perform 2D-spectropolarimetric observations of a small sunspot and ist surroundings at a heliocentric angle θ ∼ 40◦ . A long time series of about one hour has been taken scanning along the magnetic Fe i 6173 Å and the non-magnetic Fe i 5576 Å spectral lines quasi-simultaneously. Hence, with the help of image reconstruction techniques, the temporal evolution of the sunspot fine-structure in intensity as well as in velocity and magnetic field is analysed at high spatial resolution. 1 Introduction After one century of investigations on their magnetic and dynamical nature, sunspots remain enigmatic. Their evolution from pores to sunspots with developed umbra and penumbra and their stability at small scales is not well understood. There is growing evidence that, even at high spatial resolution of current spectroscopic observations, the sunspot fine-structure is still unresolved. The key for the study of the sunspot magnetic fields and the Evershed flow in the penumbra consists in spectropolarimetry at high spatial resolution. We need to obtain and to analyse the information carried by suitable spectral lines and to measure and interpret the polarised radiation coming from the solar atmosphere. Therefore, our work aims at contributing to the understanding of the sunspot fine-structure from the analysis of spectropolarimetric observations with spatial resolution better than 0.  5. 2 Observations and data analysis The observations of sunspots and surroundings were obtained with the optical setup based on the upgraded Göttingen Fabry-Perot interferometer (Puschmann et al. 2006), a Stokes V polarimeter and the Kiepenheuer Adaptive Optics System (KAOS), attached to the Vacuum Tower Telescope (Observatorio del Teide, Tenerife). The data consist of a time series (∼ 65 min) of 2D-imaging of both circularly polarised components of the light, i.e. 1 2 (I + V) and 1 2 (I − V), while scanning almost simultaneously along the magnetic sensitive Fe i 6173.3 Å (g = 2.5) and the non-magnetic Fe i 5576.1 Å (g = 0) lines. The active region NOAA 0867 was observed on April 6, 2006, when it was located at a heliocentric angle of 218 N. Bello González et al.: Temporal evolution of sunspots at high spatial resolution θ ∼ 40◦ . As shown in Fig. 1, the field of view (FOV) includes a round, symmetric sunspot accompanied by two pores nearby, at ∼ 3 distance from the penumbral border, and some others farther away (at ∼ 15 distance). Figure 1. Speckle reconstructed image of NOAA 0867 and surroundings observed on April 6, 2006. Arrow points towards disc centre and scale is given in arcseconds. Thanks to the strictly simultaneous observations of broad-band images, speckle reconstruction techniques can be applied to achieve a spatial resolution of 0.  25 for the broadband data (FOV ∼ 73 × 55 ). A similar procedure to that proposed by Puschmann & Sailer (2006) to account for the effects of the adaptive optics correction has been used. The narrowband data (FOV ∼ 29 × 50 ) are then restored (Keller & von der Lühe 1992) achieving a spatial resolution better than 0.  5 for magnetograms and velocity maps. The magnetic and velocity field calculations for the whole time series are similar to that described in Bello González et al. (2005). They consist of magnetic field measurements in the Fe i 6173 line, using the Zeeman splitting visible in the Stokes I profiles and the separation of the centre of gravity (COG method) of both circularly polarised components. The methods yield, respectively, the total magnetic field strength and the line of sight (LOS) component of the magnetic field averaged over the atmospheric region where the line is formed, i.e. mid photosphere. To estimate the velocity field, the COG method has also been applied. In this case it consists of measuring Doppler shifts from the average COG position of the 1 2 (I + V) and 1 2 (I − V) profiles of Fe i 6173 and from the Stokes I profiles of Fe i 5576, both with respect to a...

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