We present an updated version of the multilayer spectral inversion (MLSI) recently proposed as a technique to infer the physical parameters of plasmas in the solar chromosphere from a strong absorption line. In the original MLSI, the absorption prole was constant over each layer of the chromosphere, whereas the source function was allowed to vary with optical depth. In our updated MLSI, the absorption prole is allowed to vary with optical depth in each layer and kept continuous at the interface of two adjacent layers. We also propose a new set of physical requirements for the parameters useful in the constrained model tting. We apply this updated MLSI to two sets of Hα and Ca ii line spectral data taken by the Fast Imaging Solar Spectrograph (FISS) from a quiet region and an active region, respectively. We nd that the new version of the MLSI satisfactorily ts most of the observed line proles of various features, including a network feature, an internetwork feature, a mottle feature in a quiet region, and a plage feature, a superpenumbral bril, an umbral feature, and a fast down ow feature in an active region. The MLSI can also yield physically reasonable estimates of hydrogen temperature and nonthermal speed as well as Doppler velocities at different atmospheric levels. We conclude that the MLSI is a very useful tool to analyze the Hα line and the Ca ii 8542 line spectral daya, and will promote the investigation of physical processes occurring in the solar photosphere and chromosphere.

The recent study of Chae et al. (2017) found a one-to-one correspondence between plasma blobs out owing along a ray formed after a coronal mass ejection (CME) and small X-ray ares. In the present work, we have examined the spatial conguration and the eruption process of the ares that are associated with the blobs by analyzing EUV images and magnetograms taken by the SDO/AIA and HMI. We found that the main are and the successive small ares took place in a quadrupolar magnetic conguration characterized by predominant magnetic elds of positive polarity, two minor magnetic fragments of negative polarity, and a curved polarity inversion line between them, which suggests that the formation process of the blobs may be similar to that of the parent CME. We also found that the successive ares resulted in a gradual change of the quadrupolar magnetic conguration, and the relevant migration of aring kernels. The three-dimensional geometry and the property of the current sheet, that is often supposed to be embedded in an observed post-CME ray, seem to keep changing because of mutual feedback between the successive ares and the temporal change of the magnetic eld conguration. Our results suggest that the observed post-CME rays may not re ect the characteristics of the current sheet responsible for the impulsive phase of the are.

A coelostat is often used for solar observations, because it corrects the image rotation auto- matically by guiding sunlight into a fixed telescope with two plane mirrors. For the purposes of education and spectroscopic observation, the solar group at Seoul National University (SNU) plans to develop the SNU coelostat (SNUC) and install it in the SNU Astronomical Observatory (SAO). Requirements of the SNUC are < 1′′ positioning accuracy with 30 cm beam size on the entrance pupil in the compact dome. To allow for installation in the small dome, we design a compact slope type coelostat with a 45 cm primary plane mirror and a 39 cm secondary plane mirror. The motion of the SNUC is minimized by fixing the position of the slope frame. Numerical simulations of the available observational time of the designed coelostat shows that the sun can be observed ay all times from June to early August and at least three hours in other months. Since the high accuracy driving motors installed in the SNUC can be affected by external environment factors such as humidity and temperature variations, we design a prototype to test the significance of these effects. The prototype consists of a 20 cm primary plane mirror, a 1 m slope rail, a direct drive motor, a ballscrew, a linear motion guide, an AC servo motor, a reduction gear and a linear encoder. We plan to control and test the accuracy of the prototype with varying atmospheric conditions in early 2019. After testing the prototype, the SNUC will be manufactured and installed in SAO by 2020.