Fig. 3
From: A Solar cycle correlation of coronal element abundances in Sun-as-a-star observations
Photospheric to coronal abundance ratios as a function of spectral type for a sample of stars. a Logarithm of the ratio of photospheric to coronal abundance for a sample of stars as a function of spectral type. The data are adapted from Table 2 of Laming’s review16. We show the Sun as a red dot. Note that the stellar values of A c/A p represent the average of the high first ionization potential (FIP) elements C, N, O, and Ne, whereas our measurements of A c/A p are based on Ne alone. The absolute values therefore may not be directly comparable. b We show the range of values for the Sun due to the solar-cycle variation. The solid red line shows the range of movement covered by the EVE (Extreme-ultraviolet Variability Experiment) measurements. We also show the same range of cyclic movement plotted as a solid bar in the top left for comparison with the stellar measurements. The smaller error bar is the uncertainty in our composition measurements. This is the dispersion (standard deviation) in A c/A p computed from variations in the best fits to the irradiance data from a large number of random trials (see “Methods” section for more details). The green squares are three very active stars (AB Dor, AU Mic, and EK Dra) that have been excluded from similar plots in the past
