These line fluxes have been used to construct surface flux-rotation relations for solar analogs (Guinan et al., 2003). For essentially the entire rotation range of MS solar analogs, the line fluxes follow power-law relations, , with 1.8. This power-law decay is steeper than for chromospheric lines (Section 5.3), but shallower than for coronal fluxes or luminosities (recalling that the stellar radii are all close to 1 and hence the luminosities are proportional to the surface fluxes).
A very important FUV contribution comes from the H i 1216 Ly line (Ribas et al., 2005). This holds true throughout the entire MS lifetime of a solar analog although the relative contribution of this line with respect to higher-energy emission increases with age (see Table 4).
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