Abstract | In the modeling of the resonantly scattered coronal emission of neutral hydrogen and singly ionized helium, we need to know the intensity of the source, ie the chromospheric intensities. For the moment, due to a lack of full disk observations in Lyman ? 121.6 nm and Lyman ? 102.5 nm, it is commonly assumed that the chromospheric emission is uniform. In a previous study Auchère (2005) derived an empirical relation between the H I 121.6 nm and He II 30.4 nm chromomspheric intensities. The aim of the current work is to complete this previous study using spatially resolved observations in H I Lyman ? (MXUVI and CLASP) and He II 30.4 nm (EIT/SOHO and AIA/SDO). We also derive a relationship between H I Lyman ? (SUMER/SOHO) and He II 30.4 nm (EIT/SOHO). These resulting relationships will be used to use commonly available He II 30.4 nm images as proxies for H I Lyman ? or Lyman ? images for resonant scattering models. These result will be useful in order to prepare the future observations of the METIS and FSI instruments on Solar Orbiter. |
