Poster Presentation »Center-to-Limb Variation of the Velocity Field in and around a Sunspot with Light-Bridges« at SOLARNET 4
by Carsten Denker on January 17, 2017
Initial results obtained with the GREGOR Fabry-Pérot Interferometer (GFPI) during the »early science phase« with the GREGOR solar telescope were presented as a poster at the SOLARNET IV Meeting »The Physics of the Sun from the Interior to the Outer Atmosphere«, Lanzarote, Spain, 2017 January 16–20.
The disk passage of active region NOAA 12121 was observed with the 1.5-meter GREGOR solar telescope (Schmidt et al. 2012, AN 333, 796) during the time period 2014 July 22–30. On 2014 July 25 and 28, the seeing conditions were excellent so that longer time-series (30–90 min) were recorded approaching the diffraction limit of the telescope. The seeing conditions on the other days were variable ranging from mediocre to very good so that only snap-shots of high-quality images and imaging spectroscopy were possible. On each day, data were acquired with the GREGOR Fabry-Pérot Interferometer (GFPI, Denker et al. 2010, Proc. SPIE 7735, 77356M; Puschmann et al. 2012, AN 333, 880), initially in the spectral line Fe I λ630.15 nm and on the last two days in the spectral line Fe I λ617.34 nm. Imaging spectroscopy based on spectral scans restored with Multi-Object Multi-Frame Blind Deconvolution (MOMFBD, van Noort et al. 2005, SoPh 228, 191) delivered high-resolution line-of-sight (LOS) velocity maps for a field-of-view (FOV) of 50″ × 38″. In addition, we present speckle reconstructed images obtained with a G-band filter (λ430.7 nm) in the Blue Imaging Channel (BIC) of the GFPI. These images cover a FOV of 75″ × 93″ and were obtained with a cadence of about 30 s. These data serve as input for Local Correlation Tracking (LCT, November & Simon 1988, ApJ 333, 427; Verma & Denker 2011, A&A 529, A153) to investigate horizontal proper motions in and around the sunspots. The high-resolutions data are complemented by data from the Solar Dynamics Observatory (SDO, Pesnell et al. 2012, SoPh 275, 3) and Interface Region Imaging Spectrograph (IRIS, de Pontieu et al. 2014, SoPh 289, 2733). We study the evolution of the sunspots with an emphasis on growth and decay of individual sunspots, formation and dissolving of (rudimentary) penumbrae, and fine structure of light-bridges and umbral dots.
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