Carrington Maps in H i Lyα and Their Relationships with Extreme-ultraviolet and Magnetic-field Maps

Abstract

Abstract H i Lyα emission in the chromosphere and transition region is a key ingredient of the incident radiation to coronal neutral hydrogen for modeling corona Lyα emission. The Lyα emission distribution across the solar disk can be obtained from a Lyα Carrington map. Before the launch of the Advanced Space-based Solar Observatory (ASO-S), such a Lyα Carrington map was derived from the Carrington map at He ii 30.4 nm and sometimes is even assumed to be uniform. We construct the first Lyα Carrington map based on full-disk Lyα images acquired by the Solar Disk Imager (SDI) on board ASO-S and present two versions: the standard one is for a CR, and the other is daily updated. For modeling Lyα intensities during eruptions, the Carrington map with incorporated flare region is produced. Furthermore, we evaluate the difference between the Lyα Carrington map derived with SDI observations and that synthesized from the 30.4 nm data based on an empirical relationship between Lyα and He ii 30.4 nm intensities, particularly extended to flare intensities that have not been investigated before. The average difference of 38% proves the importance of the Lyα Carrington map built from observations directly. However, the synthetic Lyα Carrington map can be used as an approximation before SDI data are available. The comparison between the SDI Lyα Carrington map and the corresponding magnetic field synoptic map indicates that active regions in general are brighter in Lyα, while the sunspot umbras with strong magnetic field strength are usually weaker in Lyα.