Abstract
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)
Highlights
A major objective of the Far Ultra Violet instrument (FUV) on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission is the observation of the global distribution of the electron and proton auroras in parallel with large-scale changes in the magnetosphere
We describe a methodology allowing for the extraction of the parameters of proton precipitation using SI12 and Wide-band Imaging Camera (WIC) imaging of proton-dominated auroral regions and discuss sources of uncertainties and errors
We show that IMAGE-FUV global imaging may be used to map and remotely determine proton precipitation flux and characteristic energy values consistent with in situ particle measurements
Summary
2001; Mende et al, 2001). An important feature of the Far Ultraviolet imager is its capability to simultaneously image the aurora in three wavelength regions (Mende et al, 2000). Earlier studies of the morphology and dynamics of the proton aurora with SI12 images (Immel et al, 2002; Burch et al, 2002) have revealed the presence of detached subauroral proton arcs in the afternoon and dusk sectors of the Northern Hemisphere under changing interplanetary magnetic field (IMF) conditions. Coumans et al (2002) have shown that protons with energies above 30 keV, the upper limit of the DMSP and FAST particle detectors, may play a significant role in the excitation of the equatorward regions of the proton aurora, in the afternoon sector. We show that IMAGE-FUV global imaging may be used to map and remotely determine proton precipitation flux and characteristic energy values consistent with in situ particle measurements
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