General Formation Properties of the O I 1027 and 1028 Å lines near the Lyman β for the Diagnostics with Solar-C_EUVST

We consider that the neutral oxygen doublet lines O I 1027 and 1028Å are good candidates for understanding the properties of the chromosphere and transition region when these lines are combined with Lymanβ. The latter is a strong candidate of the upcoming solar mission Solar-C_EUVST while the former lines are located in its wing. In this work, we examine general spectroscopic properties of those lines in the quiet sun by synthesizing them assuming non-local thermal equilibrium conditions and partial redistribution effects. We estimate the heights where the spectral lines are sensitive to the physical parameters with a 1D semi-empirical atmospheric model. Furthermore, we synthesize the intensity spectrum using the 3D "enhanced network" simulation computed with the Bifrost RMHD code. The average formation height of Lymanβ is about 2400 km, where temperature is ~2×10^4 K. The O I 1027 and 1028 Å lines form at about 1650 and 1500 km in average, respectively, in the upper chromosphere where its temperature is ~8×10^3 K. The spatial distribution of signals confirms that the lines are sensitive to the thermodynamics of the solar atmosphere at lower layers than those covered by the Lymanβ. These results indicate that the O I lines of interest are good candidates for EUV spectroscopy and complement the Lymanβ line bringing the possibility of simultaneous multi-layer observations. We expect that these spectral lines will give us more possibilities to infer complex dynamic phenomena occurring in the lower atmosphere (e.g. Ellerman Bombs and UV bursts).