U.: Remote sensing of the proton aurora characteristics from IMAGE-FUV, Ann

Abstract. The combination of simultaneous global images of the north polar region obtained with the IMAGE-FUV imaging system makes it possible to globally map the proper-ties of the electron and proton auroral precipitation. The SI12 imager, which observes the Doppler-shifted Lyman-α emis-sion, provides a global snapshot of the proton aurora every 2 min. These images may be combined with those from the Wide-band Imaging Camera (WIC), to remotely characterize the proton precipitation in proton-dominated auroral struc-tures frequently observed in the afternoon and pre-midnight sectors at the equatorial edge of the auroral oval. It is shown that both the proton energy flux and the mean energy deter-mined by this method are in good agreement with coincident in situ measurement from low altitude satellites carrying pro-ton detectors, when taking into account the different spatial resolution of the two types of observations. Four proton-dominated cases are illustrated in this study. They belong to two categories of proton auroral features: (i) hydrogen arcs known to occur in the evening sector equatorward of the electron oval and (ii) detached proton arcs observed with IMAGE-FUV in the afternoon sector following changes in orientation of the interplanetary magnetic field. They are characterized by a proton flux of 0.5–2 mW m−2 and a mean energy in the range 10–17 keV. Key words. Magnetospheric physics (auroral phenomena; energetic particles, precipitating; magnetopause, cusp, arid boundary layers)