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 für 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 Lüehe 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 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.