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Using a New Sky Brightness Monitor to Observe the Annular Solar Eclipse on 15 January 2010  

Yu Liu   Submitted: 2012-04-19 20:44

For the future development of Chinese Giant Solar Telescope (CGST) in Western China, a new sky brightness monitor (SBM) has been produced for the site survey for CGST. To critically examine the performance and sensitivity of SBM, we used it in the observation of the annular solar eclipse in Dali City, Yunnan, on 15 January 2010. The observation met good weather condition with almost clear sky during the eclipse. The SBM measurement translates into the solar illuminance changes at a level of 2.4X10-4 I s^-1 during the eclipse. The time of the minimal sky brightness in the field of view is found consistent with the time of maximum eclipse. Two local sky regions in the FOV are chosen to make time series of calibrated skylight profiles. The evolution of the sky brightness thus calibrated also shows good consistency with the eclipse, particularly between the second and the third contacts. The minimal sky brightness in each local sky region took place within half a minute from the corresponding predicted contact time. Such small time delays were mainly caused by occasional cirri. The minimal sky brightness measured during the eclipse is a few millionths of I_sun with standard deviation of 0.11 millionths of I_sun. The observation supports that the singlescattering process (optically thin conditions) is the main contributor to the atmospheric scattering. We have demonstrated that many important aerosol optical parameters can be deduced from our data.We conclude that the new SBM is a sensitive sky photometer that can be used for our CGST and coronagraph site surveys.

Authors: Y. Liu, Y.-D. Shen, X.-F. Zhang, N.-P. Liu
Projects: None

Publication Status: Accepted for publishing in Solar Physics
Last Modified: 2012-04-20 08:54
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Yu Liu   Submitted: 2008-03-24 15:59

Recent advances have made it possible to obtain two-dimensional line-of-sight magnetic field maps of the solar corona from spectropolarimetric observations of the FeXIII 1075 nm forbidden coronal emission line. Together with the linear polarization measurements that map the azimuthal direction of the coronal magnetic field projected in the plane of the sky containing Sun center, these coronal vector magnetograms allow for direct and quantitative observational testing of theoretical coronal magnetic field models. This paper presents a study testing the validity of potential-field coronal magnetic field models. We constructed a theoretical coronal magnetic field model of active region AR 10582 observed by the SOLARC coronagraph in 2004 by using a global potential field extrapolation of the synoptic map of Carrington Rotation 2014. Synthesized linear and circular polarization maps from thin layers of the coronal magnetic field model above the active region along the line of sight are compared with the observed maps. We found that the observed linear and circular polarization signals are consistent with the synthesized ones from layers located just above the sunspot of AR 10582 near the plane of the sky containing the Sun center.

Authors: Yu Liu, and Haosheng Lin
Projects: STEREO

Publication Status: accepted by ApJ
Last Modified: 2008-09-23 21:12
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Using a New Sky Brightness Monitor to Observe the Annular Solar Eclipse on 15 January 2010
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