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NOAO Newsletter - NOAO Highlights - September 2000 - Number 63


NSO Adaptive Optics Operating Successfully at the Dunn Solar Telescope and the German VTT

Michael Sigwarth, Thomas Rimmele, Kit Richards, Richard Radick, Klaus Hartkorn, Kai Langhans, and Wolfgang Schmidt

Significant progress continues to be made with the NSO low-order adaptive optics (AO) system; there have been several successful scientific observing runs at the Dunn Solar Telescope (DST) since the first "closed-loop" run in September 1998 (see NOAO Newsletter, No. 56). Examples of observing runs in 1999 and early 2000 can be found at http://www.noao.edu/noao/staff/keller/aopds/index.html and http://www.sunspot.noao.edu/PPAGES/sigwarth/results/2daospec.html.

Klaus Hartkorn and Kai Langhans of the Kiepenheuer-Institut fr Sonnenphysik (KIS) used the NSO AO system at the DST in March to study the very small magnetic field concentrations in the solar photosphere. By using the NSO Universal Birefringent Filter and a fast Speckle camera system from KIS, Hartkorn and Langhans were able to observe structures at the diffraction limit of the DST in the blue spectral range (G-Band 430 nm) of 0.13", corresponding to a physical scale of 100 km.

Each data set of the spectrometer observations consists of 18 filtergrams and continuum images, each with 1.5 sec integration time (30 sec to complete a line scan). The AO system allowed the observers to obtain a consistent spatial resolution of about 0.25", or 180 km, throughout several line scans.

As part of a joint effort involving NSO, Big Bear Solar Observatory (BBSO), and KIS to design and build high-order AO systems, the NSO low-order AO system was shipped this spring to the Observatorio del Teide in Tenerife, Spain. In early April 2000, Thomas Rimmele (NSO) and Kit Richards (NSO), with colleagues from KIS, integrated the system at the 70-cm German Vacuum Tower Telescope (VTT). The NSO AO system worked flawlessly from the first day of the observing campaign through the end of the run in June, demonstrating that it can be successfully adapted at other solar telescopes. KIS Director Oskar von der Lehe summarized his experience with this AO system with the following statement: "If you have observed once with AO, you don't want to observe any longer without [it]."

At the end of April 2000, during the first AO observing campaign at the German VTT, Michael Sigwarth (NSO), Wolfgang Schmidt (KIS), and Kai Langhans (KIS) carried out high-resolution 2D spectroscopic observations with the KIS Triple-Etalon Solar Spectrometer (TESOS), the KIS Speckle camera system, and the NSO AO system to investigate the development and flow pattern of young active regions. Additional observing campaigns were conducted to study, for example, the dynamics and origin of G-Band bright points, the development of sunspot penumbrae, and the nature of Evershed flows, granular dynamics, and sunspot oscillations.

The AO system is now back at the DST in Sunspot, where several observing runs using the system have been scheduled and requested for the third and fourth quarters of 2000.

The original data and additional examples of these observations can be found at http://www.kis.uni-freiburg.de/~kai/sac_peak/recent.html.

Caption: This image, taken with the NSO low-order AO system at the German VTT in Tenerife, shows the few-hours-old active region NOAA 8965 close to disc-center, observed on 22 April 2000, between 15:00 and 16:00 UT (north is up; east is right). The underlying image was selected from a burst of images taken in the G-Band (430 nm) with a fast Speckle camera system at 5 ms integration time. At this wavelength, magnetic flux concentrations show up as "bright points." The circular field-of-view data were obtained with the narrow band (20 m) filter-spectrometer TESOS. They show continuum images taken at 550 nm and the corresponding Dopplergrams obtained from the line core shifts of Fe I 557 nm for each data point (bright are up flows; dark are down flows). Elongated features probably correspond to areas where new magnetic flux appears. Strong down flows in these areas can occur when convective instability exists within the magnetic field. These comments are based on preliminary data calibration and analysis.


Caption: This 14 x 9" (10,150 x 6500 km) area of the solar photosphere shows the morphology of G-Band (430 nm) bright points, which are small magnetic flux concentrations that show up as brightening at very high spatial resolution. Some bright points appear to be at the edges of granules, while others are situated in the dark intergranular lanes. A "Crinkel" (bent arc) feature is visible at position (6,2). It seems to originate in the granule on the right and overlap the granule on the left. These data were obtained on 15 March 2000 by K. Hartkorn (KIS), K. Langhans (KIS), and T. Rimmele (NSO) et al. at the DST with the KIS Dalsa Speckle camera system and the NSO low-order AO system.


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