Progress of site survey for large solar telescopes in western China

Abstract

Excellent sites are necessary for developing and installing ground-based large telescopes. For very-high-resolution solar observations, it had been unclear whether there exist good candidate sites in the west areas in China, including the Tibetan Plateau and the Pamirs Plateau. The project of solar site survey for the next-generation large solar telescopes, i.e., the Chinese Giant Solar Telescope (CGST) and the large coronagraph, has been launched since 2011. Based on the close collaboration among Chinese solar society and the scientists from NSO, HAO and other institutes, we have successfully developed the standard instruments for solar site survey and applied them to more than 50 different sites distributed in Xinjiang, Tibet, Qinghai, Sichuan, Yunnan and Ningxia provinces. We have built two long-term monitoring sites in Tibet and the large Shangri-La to take systematic site data. Clear evidence, including the key parameters of seeing factor, sky brightness and water vapor content, has indicated that a few potential sites in the large Tibetan areas should obtain the excellent astronomical conditions for our purpose to develop CGST and large coronagraph. We introduce the fresh site survey results in this report.

Modeling Viscosity of High Titania Slag

“…Until recent years, several researchers have begun to study the viscosity of high-titania slags again. In our previous work, [3,8] we measured viscosities of 24 different synthetic high TiO 2 slags (45 to 88 mass pct TiO 2 ) and reached some similar conclusions with the early studies mentioned above. [2,6,7] However, our previous experimental viscosity values (around 0.65 dPa s) were slightly higher than those in the mentioned literature.…”

“…Therefore, the viscosity data with no specific compositions and temperature information were not considered in this work. It should be noted that the viscosity data published by Li et al [8] related to the TiO 2 -FeO-X(CaO, SiO 2 , MgO) ternary slag system containing CaO (0.5 to 2 mass pct), SiO 2 (2 to 6 mass pct), and MgO (1to 4 mass pct), respectively. However, a small amount of (CaO, SiO 2 , MgO) just had a slight influence on the viscosity compared to the TiO 2 -FeO binary slag system in this work.…”

“…[23] In the present work, the viscosities of TiO 2 -FeO and TiO 2 -FeO-Ti 2 O 3 slags were measured experimentally using the rotating cylinder method under argon atmosphere. The present measurements together with our previous measurements as well as the literature data [8][9][10]24] were used to optimize the present viscosity model. This model was developed according to the modification of the Vogel [25] -Fulcher [26] -Tammann [27] (VFT) semi-empirical formalism.…”

The morphological comparison and analysis of coronal green line

“…At the same time, combining the observations of SDO with our coronagraph data, it is convenient for us to comparison and analysis the coronal loops. At the same time, it also revealed the structure of the solar field that we can hardly observe directly in normal time (Rosner et al 1978).In China NSFC (11533009, 11503084) has been supported aiming to find excellent sites to build large coronagraphs (Liu et al 2016).…”

The coronal green line monitoring: a traditional but powerful tool for coronal physics

“…Although the maintenance and running of a ground-based coronagraph station is hard due to the high altitudes and sometimes shortage of funding, more and more scientists have realized that keeping the long-term and high-resolution for coronal observations is critical for better understanding solar cycles as well as stellar coronal physics. A site survey project (11533009 NSFC) has been supported aiming to find excellent sites in western China to build large coronagraphs (Liu et al 2016).…”