The electron and proton aurora as seen by IMAGE-FUV and FAST

The Far Ultraviolet Instrument (FUV) on the IMAGE spacecraft observes the a urora in three different channels. One of them (SI12) is sensitive to the s ignal from precipitating protons, while the other two (WIC and SI13) observ e auroral emissions which are not only excited by precipitating electrons, but also by protons. We examine a period when in-situ particle measurements by the FAST spacecraft were available simultaneously with global imaging w ith FUV. The measured electron and proton energy spectra are used to calcul ate the auroral brightness along the FAST orbit. The comparison with the FU V/IMAGE observations shows good quantitative agreement and demonstrates tha t under certain circumstances high proton fluxes may produce significant am ounts of auroral FUV emission.