The Carrington Map in H I Ly-alpha Passband Based on ASO-S/LST/SDI

The Lyman-alpha (Lyα) Solar telescope (LST) is one of the three payloads onboard the Advanced Space-based Solar Observatory (ASO-S) mission. As one of the instruments of LST, the Solar Disk Imager (SDI) works in the Lyα waveband of 121.6 ± 10nm with a field of view (FOV) up to 1.2 R⊙. In this work, we construct the Carrington maps (or so-called synoptic map) of solar Lyα intensities based on full-disk images acquired by SDI. We present two versions of Carrington maps, one is synthesized once in a Carrington cycle, and the other is daily-updated. The former gives the general view of the emission distribution in Lyα during the whole CR, while the latter provides a better near-real-time measurement of the intensity. By establishing the relation between the emission of Lyα in 121.6 nm and He II in 30.4 nm, we provide a possible way to offset the observation gaps of SDI from AIA/304 channel. The radiometric calibration is performed using the cross-calibration method with GOES/EUVS data. To this end, the calibrated carrington map can be applied to constrain the incident emission to the corona in Lyα. Regarding this application, we propose an upgraded version of the carrington map to correct the emission variation caused by eruptions like coronal mass ejections (CMEs) and flares. The comparison between the SDI Carrington map and the magnetogram synoptic map serves as the final example of the application of SDI Carrington map in our work, the locations of different features in line-of-sight magnetic field and in Lyα are directly compared.