A comparison of solar and stellar ultraviolet spectra obtained with SKYLAB and IUE.

Abstract

A comparison is presented of 78 Short-Wavelength Primary (SWP) low-resolution IUE spectra of 45 late-type stars and 10 high-resolution Skylab spectra of spatially-resolved solar regions of various degrees of magnetic activity, including quiet areas, plage regions, and one flare. The results show that the different levels of chromospheric and transition region emission observed in stars of similar spectral types are paralleled by a similar behavior displayed by solar regions of different magnetic activity and that the spatially-resolved solar data obey the same flux-flux relationships as the stellar data over more than three order of magnitude. It is argued that the similar behavior of the solar and stellar UV line fluxes, together with the dependence of the stellar fluxes on rotation, presents an evidence that stellar activity is of magnetic origin and likely results from a dynamo process.