Remote sensing of the proton aurora characteristics from IMAGE-FUV

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 properties of the electron and proton auroral precipitation. The SI12 imager, which observes the Doppler-shifted Lyman-a emission, 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 structures 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 determined by this method are in good agreement with coincident in situ measurement from low altitude satellites carrying proton 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 mWm^-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)