References of "Gérard, Jean-Claude"
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See detailUltraviolet emissions from the magnetic footprints of Io, Ganymede and Europa on Jupiter
Clarke, J. T.; Ajello, Joseph M.; Ballester, G. et al

in Nature (2002), 415(6875), 997-1000

Io leaves a magnetic footprint on Jupiter's upper atmosphere that appears as a spot of ultraviolet emission that remains fixed underneath Io as Jupiter rotates(1-3). The specific physical mechanisms ... [more ▼]

Io leaves a magnetic footprint on Jupiter's upper atmosphere that appears as a spot of ultraviolet emission that remains fixed underneath Io as Jupiter rotates(1-3). The specific physical mechanisms responsible for generating those emissions are not well understood, but in general the spot seems to arise because of an electromagnetic interaction between Jupiter's magnetic field and the plasma surrounding Io, driving currents of around 1 million amperes down through Jupiter's ionosphere(4-6). The other galilean satellites may also leave footprints, and the presence or absence of such footprints should illuminate the underlying physical mechanism by revealing the strengths of the currents linking the satellites to Jupiter. Here we report persistent, faint, far-ultraviolet emission from the jovian footprints of Ganymede and Europa. We also show that Io's magnetic footprint extends well beyond the immediate vicinity of Io's flux-tube interaction with Jupiter, and much farther than predicted theoretically(4-6); the emission persists for several hours downstream. We infer from these data that Ganymede and Europa have persistent interactions with Jupiter's magnetic field despite their thin atmospheres. [less ▲]

Detailed reference viewed: 27 (12 ULiège)
See detailThe Electron and Proton Energy Input Into The Auroral Thermosphere During Substorms: Remote Sensing With Image-fuv
Hubert, Benoît ULiege; Gérard, Jean-Claude ULiege; Meurant, M. et al

in EGS XXVII General Assembly, Nice, 21-26 April 2002 (2002)

This paper investigates the dynamical properties of the Eta model, a state-of-the- art nested limited-area model, following the approach previously developed by the present authors. It is first shown that ... [more ▼]

This paper investigates the dynamical properties of the Eta model, a state-of-the- art nested limited-area model, following the approach previously developed by the present authors. It is first shown that the intrinsic dynamics of the model depends crucially on the size of the domain, with a non-chaotic behavior for small domains, supporting earlier findings on the absence of sensitivity to the initial conditions in these models. The quality of the predictions of several Eta model versions differing by their domain size is next evaluated and compared with the Avn analyses on a targeted region, centered on France. Contrary to what is usually taken for granted, a non-trivial relation between predictability and domain size is found, the best model versions be- ing the ones integrated on the smallest and the largest domain sizes. An explanation in connection with the intrinsic dynamics of the model is advanced. [less ▲]

Detailed reference viewed: 10 (0 ULiège)
See detailIonospheric Conductances Due To Auroral Proton and Electron Precipitation Deduced From Image-fuv Observations.
Coumans, Valérie ULiege; Hubert, Benoît ULiege; Meurant, M. et al

in EGS XXVII General Assembly, Nice, 21-26 April 2002 (2002)

The FUV instrument on the IMAGE (Imager for Magnetopause-to-Aurora Global Ex- ploration) satellite monitors the aurora in three different spectral regions. The Wide- band Imaging Camera (WIC) observes the ... [more ▼]

The FUV instrument on the IMAGE (Imager for Magnetopause-to-Aurora Global Ex- ploration) satellite monitors the aurora in three different spectral regions. The Wide- band Imaging Camera (WIC) observes the molecular N2 LBH and the atomic NI emissions at 140-180 nm. The two channels of the Spectrographic Imager (SI) ob- serve the Doppler shifted Lyman- emission at 121.8 nm due to precipitating protons (SI12) and the electron auroral emission of OI at 135.6 nm (SI13). We calculate the Pedersen and Hall ionospheric conductances due to auroral particles based on FUV observations separately for the proton and electron precipitation. We first estimate the electron and proton energy fluxes from the FUV data, relying on energy degradation and auroral emission models. A two-stream model is used for the electron aurora while the proton aurora modeling is based on the direct Monte Carlo method, which gives a stochastic solution to the Boltzmann equations for the H+ - H beam. The electron energy is evaluated by combining observations from the three FUV instruments. For the proton energy, we use a statistical model based on in-situ particle measurements. Second, the particle energy and energy flux are used to estimate the ionization rates separately for protons and electrons, consistently with the energy degradation models. Finally, the electron and ion densities are estimated from ionization profiles, and the Pedersen and Hall conductances are calculated from fundamental equations. Appli- cations of the method to the distribution of the conductance at winter solstice in the course of substorm development over the north polar region will be illustrated. [less ▲]

Detailed reference viewed: 10 (1 ULiège)
See detailCharacteristics and Cause of Localized Auroral Uv Emission At High Latitude
Frey, H. U.; Mende, S. B.; Immel, T. J. et al

in EGS XXVII General Assembly, Nice, 21-26 April 2002 (2002)

The FUV instrument on IMAGE frequently observes localized ultraviolet emission at high latitudes, poleward of the general auroral oval. These localized emissions occur during northward IMF conditions and ... [more ▼]

The FUV instrument on IMAGE frequently observes localized ultraviolet emission at high latitudes, poleward of the general auroral oval. These localized emissions occur during northward IMF conditions and there are two different types of them. One type is especially distinct in the observations of Doppler shifted Lyman alpha emission from proton precipitation. This type occurs during high solar wind dynamic pressure. We interpret this emission as the optical signature of proton precipitation into the cusp after lobe reconnection at the magnetopause. The second type of localized emission is distinct in the wide-band (WIC) and oxygen (SI13) images, but is absent in the proton images. This emission occurs during positive IMF By, but very low solar wind density and dynamic pressure. We interpret this emission as the optical signature of electron acceleration in the upward part of a field aligned current circuit after reconnection. [less ▲]

Detailed reference viewed: 11 (1 ULiège)
See detailThe IMAGE mission (NASA) : design, test and results from the far UV spectrographic Imager
Habraken, Serge ULiege; Renotte, Etienne ULiege; Jamar, Claude ULiege et al

in Space scientific research in Belgium (Space Sciences) (2002)

Detailed reference viewed: 29 (10 ULiège)
See detailSimultaneous Observation of Magnetospheric Neutral Atoms and Proton Aurora
Mende, S. B.; Frey, H. U.; Immel, T. J. et al

in Eos (2001), 42

Data from the High Energy Neutral Atom (ENA) and the far ultraviolet (FUV) imagers on IMAGE were compared for a six hour period during which a reasonably intense substorm occurred. The substorm presented ... [more ▼]

Data from the High Energy Neutral Atom (ENA) and the far ultraviolet (FUV) imagers on IMAGE were compared for a six hour period during which a reasonably intense substorm occurred. The substorm presented is typical of a substorm expansive phase showing that while the total electron precipitation suddenly increase one whole order of magnitude, the protons increase only about 50%. In principle ENA images represent the trapped fluxes in the magnetosphere while the proton aurora measured by the FUV SI12 instrument represents the precipitating component. At substorm onset the increase in intensity of the auroral protons and electrons is very sudden while the intensification of the ENA-s coming from regions of L<6 is much more gradual. The intensification of the precipitating electrons is relatively short lived ( ~ 10 minutes) while the ENA enhancements are long lived (almost a whole hour). Just prior to the substorm expansive phase (in the growth phase) the precipitated proton and electron fluxes encounter a minimum while the ENA-s show a slight growth. [less ▲]

Detailed reference viewed: 42 (11 ULiège)
See detailTwo types of localized auroral UV emission on the dayside
Frey, H. U.; Mende, S. B.; Immel, T. J. et al

Conference (2001, December 01)

The FUV instrument on IMAGE frequently observes localized ultraviolet emission on the high latitude dayside, poleward of the normal auroral oval. There are two different types of these localized emissions ... [more ▼]

The FUV instrument on IMAGE frequently observes localized ultraviolet emission on the high latitude dayside, poleward of the normal auroral oval. There are two different types of these localized emissions. One is especially distinct in the observations of Doppler shifted Lyman alpha emission from proton precipitation. This type occurs during northward IMF and high solar wind dynamic pressure. We interpret this emission as the optical signature of proton precipitation into the cusp after lobe reconnection at the magnetopause. The second type of localized emission is visible in the wide-band (WIC) and oxygen (SI13) imagers, but is absent in the proton imager. This emission occurs during northward IMF but very low solar wind density and dynamic pressure. We interpret this emission as the optical signature of electron acceleration after reconnection. [less ▲]

Detailed reference viewed: 39 (9 ULiège)
Peer Reviewed
See detailAuroral Precipitation during the Bastille Day Storm Recovery
Immel, T. J.; Mende, S. B.; Frey, H. U. et al

Conference (2001, December 01)

The recovery period following the geomagnetic storm of July 15-16, 2000 is marked by rapid changes in auroral morphology and brightness in the sunlit hemisphere. These observations are made by the FUV and ... [more ▼]

The recovery period following the geomagnetic storm of July 15-16, 2000 is marked by rapid changes in auroral morphology and brightness in the sunlit hemisphere. These observations are made by the FUV and EUV imagers aboard the IMAGE satelite. Clear signatures of magnetospheric convection are observed in the motion of the auroral forms, indicating sunward convection of plasma in the polar cap under the strong northward component of the IMF. Precipitation is also observed equatorward of the auroral oval on the dayside in large diffuse arcs. Unlike previously observed detached proton arcs, this precipitation appears to have a significant electron component. Determination of the characteristic energies and fluxes of electrons and protons requires the proper removal of FUV airglow emissions, which in this case have been strongly affected by the recent magnetic activity. EUV images provide a very clear signature of these events, with practically no airglow contamination. With proper modeling, these EUV images could provide improvements to the characterization of the magnetospheric energy input to the thermosphere and ionosphere from space-based imaging. [less ▲]

Detailed reference viewed: 35 (4 ULiège)
Peer Reviewed
See detailObservation of the proton aurora with IMAGE FUV imager and simultaneous ion flux in situ measurements
Gérard, Jean-Claude ULiege; Hubert, Benoît ULiege; Meurant, M. et al

in Journal of Geophysical Research. Space Physics (2001), 106(A12), 28939-28948

The far ultraviolet cameras on board the IMAGE satellite images the aurora in three different spectral regions. One of the channels of the spectrographic imager SI12 observes the Doppler-shifted Lyman ... [more ▼]

The far ultraviolet cameras on board the IMAGE satellite images the aurora in three different spectral regions. One of the channels of the spectrographic imager SI12 observes the Doppler-shifted Lyman alpha emission of precipitating protons. It makes it possible to spectrally discriminate between the proton and electron FUV aurora and to globally map the energetic protons. Its response depends on the auroral Lyman alpha. line shape which reflects the characteristics of the proton pitch angle and energy distributions. We illustrate the dependence of the SI12 count rate on the characteristic energy of the proton precipitation and the viewing geometry. Simultaneous in situ observations of the precipitated protons have been collected during a FAST satellite pass when IMAGE was observing the global north polar region. The premidnight region located at the equatorward boundary of the oval is dominated by proton precipitation with a mean energy E = 7 keV which is separated from the electron component. The prenoon crossing exhibits a softer proton energy spectrum with E = 0.9 keV. The measured proton energy distribution is used as an input to a Monte Carlo model to calculate the expected SI12 signal along the magnetic footprint of the satellite orbit. If the different spatial resolution of the two types of measurements is accounted for, a good quantitative agreement is found with the IMAGE observations. Similarly, ion flux measurements collected on board the Defense Meteorological Satellite Program F15 satellite during an overflight in the postmidnight sector provide good agreement with the SI12 observations at the footprint aurora. The comparisons confirm the reliability of the FUV IMAGE cameras to remotely discriminate between the electron and the proton precipitations. The vertical emission rate profiles of the N-2 Lyman-Birge-Hopfield and O I (1356 Angstrom) emissions are calculated in the proton-dominated premidnight region. It is shown that the protons and the electrons produce FUV emissions with contributions peaking at different altitudes. Excitation by secondary electrons dominates the production of both emissions. [less ▲]

Detailed reference viewed: 48 (13 ULiège)
See detailSpatial and temporal variations of the Jovian auroral electrons deduced from HST-STIS ultraviolet spectroscopy
Gérard, Jean-Claude ULiege; Gustin, Jacques ULiege; Grodent, Denis ULiege et al

in Bulletin of the American Astronomical Society (2001, November 01)

Jovian auroral spectra have been observed with the Space Telescope Imaging Spectrometer (STIS) in both hemispheres since 1997, including during the recent Cassini Jupiter millenium campaign. The time ... [more ▼]

Jovian auroral spectra have been observed with the Space Telescope Imaging Spectrometer (STIS) in both hemispheres since 1997, including during the recent Cassini Jupiter millenium campaign. The time-tagged G140L STIS spectra used for this study cover the 1100-1700 Ì· range which includes the Lyman (B-X) bands and continuum and the Werner (C-X) bands. Time-dependent spectroscopy with spatial resolution along the 25 arcsec slit makes it possible to follow spectral and temporal variations in different regions of the aurora. FUV images observed on the same HST orbit were obtained to put the spectral data into the global morphology context. Synchronous observations of spectral domains absorbed or not by CH4 and other hydrocarbons are used to determine the FUV color ratio and the depth of the auroral emission relative to the methane homopause. Large variations of the color ratio across the auroral oval are observed. The time evolution of the mean electron energy and its possible correlation with the precipitated energy flux are investigated. It is found that the mean electron energy generally positively correlates with the auroral brightness. In contrast, flares occasionally observed in the polar cap can correspond to a softening or a hardening of the precipitation. The mean electron energy associated with the Io trail is approximately constant and shows less hydrocarbon absorption than the higher latitude aurora. [less ▲]

Detailed reference viewed: 8 (4 ULiège)
See detailHST Observations of Aurora from the Magnetic Footprints of Io, Ganymede, and Europa during the Millennium Campaign
Clarke, J. T.; Grodent, Denis ULiege; Connerney, J. et al

in Bulletin of the American Astronomical Society (2001, November 01)

UV images of Jupiter's aurora obtained with the HST STIS instrument reveal much detail in the distribution of emissions from Io's magnetic footprint on Jupiter, including extended trails of emission in ... [more ▼]

UV images of Jupiter's aurora obtained with the HST STIS instrument reveal much detail in the distribution of emissions from Io's magnetic footprint on Jupiter, including extended trails of emission in the downstream direction. Emissions are also seen from the magnetic footprints of Ganymede and Europa, relatively much fainter and point-like in spatial extent. Knowledge of the statistical properties of these emissions, in terms of their locations and brightnesses, was greatly advanced in a comprehensive series of images obtained during the Millennium campaign in Dec. 2000 - Jan. 2001. These images provide sufficient spatial coverage to give a good indication of the auroral oval locations mapping to Io and Ganymede, and a few points mapping to Europa. The observed variations in footprint properties provide indications of the nature of the electrodynamic interactions of the satellites with Jupiter's magnetic field. These and other indicators also show the direction that magnetic field models should take to better describe Jupiter's internal magnetic field. Contributing evidence comes from the locus of footprint latitudes, and their deviations from the VIP4 model. The latitudinal distance between the Io and Ganymede footprint loci indicates variations in the local field strength, with larger separations corresponding to a weaker field. These separations, and the distance from and distortion of the main oval, indicate an anomalously weak field region in the north near 90[SUP]o[/SUP] longitude. This work has been supported by NASA in STScI grants GO-08171-97A and GO-08657-01A to the University of Michigan. [less ▲]

Detailed reference viewed: 36 (2 ULiège)
See detailH[SUB]2[/SUB] temperature and self-absorption: analysis of Jovian auroral spectra obtained with the FUSE satellite
Gustin, Jacques ULiege; Feldman, P. D.; Gérard, Jean-Claude ULiege et al

in Bulletin of the American Astronomical Society (2001, November 01)

High-resolution spectra of the Jovian aurora have been obtained with unprecedented spectral resolution in the 900-1190 Ì· window with the the Far Ultraviolet Spectroscopic Explorer (FUSE), using the 30 ... [more ▼]

High-resolution spectra of the Jovian aurora have been obtained with unprecedented spectral resolution in the 900-1190 Ì· window with the the Far Ultraviolet Spectroscopic Explorer (FUSE), using the 30"x30" LWRS aperture. All observed features belong to the H[SUB]2[/SUB] transitions from the B, C, B', D, B" and D' electronic states to the ground-state. These emissions are excited by inelastic collisions of the primary and secondary auroral electrons with H[SUB]2[/SUB] molecules. The relative intensity distribution of the observed lines depends on the rotational temperature of the emitting layer and self-absorption. Below 1100 Ì· , the transitions leading to the v" = 0, 1 and 2 levels of ground-state are partially or totally absorbed by H[SUB]2[/SUB], giving indications about the vibrational H[SUB]2[/SUB] distribution and overlying column. After a validation with an unabsorbed and a self-absorbed laboratory spectrum obtained in controlled conditions (100K, 300 eV), this study compares the observations and synthetic spectra, generated by a code including the B, C and B', D, B" and D' Rydberg states. The rotational and vibrational H[SUB]2[/SUB] temperatures are determined as well as the overlying H[SUB]2[/SUB] column. The combination of these parameters is used to determine the depth of the auroral energy deposition. This work is based on data obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by the Johns Hopkins University. French participants are supported by CNES. Financial support to U.S. participants has been provided by NASA contract NAS5-32985. [less ▲]

Detailed reference viewed: 35 (2 ULiège)
See detailHigh color ratio and high temperature in Jupiter's auroral atmosphere
Grodent, Denis ULiege; Gustin, Jacques ULiege; Gérard, Jean-Claude ULiege et al

Poster (2001, October 27)

A high FUV color ratio usually implies that most of the energy of the impinging auroral particles is deposited below the methane homopause. In this region, the resulting auroral heating is efficiently ... [more ▼]

A high FUV color ratio usually implies that most of the energy of the impinging auroral particles is deposited below the methane homopause. In this region, the resulting auroral heating is efficiently balanced by the strong hydrocarbon cooling. Therefore, this auroral process cannot sustain the high temperature observed in the Jovian auroral atmosphere. This work is an attempt to remove the ambiguity between the high color ratios and high temperatures deduced from the HST data. In order to study this apparent contradiction, the two-stream energy deposition model described by Grodent et al. (2001) has been upgraded with a Joule heating module and an adiabatic cooling approximation. The most recent hydrocarbon auroral density profiles have been included. A new EUV-FUV spectral generator has been developed and allows one to consider new observational constrains, such as the very high H2 scale heights deduced from the Cassini-Jupiter flyby HST observations. [less ▲]

Detailed reference viewed: 14 (2 ULiège)
Peer Reviewed
See detailThe role of proton precipitation in the excitation of auroral FUV emissions
Hubert, Benoît ULiege; Gérard, Jean-Claude ULiege; Bisikalo, D. V. et al

in Journal of Geophysical Research (2001), 106

Far ultraviolet remote sensing from a high-altitude satellite is extensively used to image the global aurora, derive its energetics, and follow its dynamical morphology. It is generally assumed that the ... [more ▼]

Far ultraviolet remote sensing from a high-altitude satellite is extensively used to image the global aurora, derive its energetics, and follow its dynamical morphology. It is generally assumed that the observed emissions are dominated by the interaction of the precipitated electrons with the thermospheric constituents. A model to calculate far ultraviolet emissions excited by auroral electrons and protons and the secondary electrons they generate has been used to calculate the volume excitation rate of the H I Ly-alpha, O I 1304 and 1356 Å, N I 1493 Å multiplets, and the N[SUB]2[/SUB] Lyman-Birge-Hopfield (LBH) bands. The characteristic energy and the energy flux are derived from the observed statistical distribution of precipitated protons and electrons. This model is applied to the midnight aurora, the noon cusp, and a proton-dominated aurora for moderately disturbed conditions. We show that in the first two cases, direct electron impact dominates the vertically integrated emission rate over the proton component, although proton excitation plays an important role at some altitudes in the daytime cusp. In afternoon regions of the auroral zone near the auroral boundary, secondary electrons due to proton ionization are the main source of FUV emissions. The energy dependence of the efficiency of LBH band emission viewed from high altitude is calculated for electron and proton precipitations. Maps of the N[SUB]2[/SUB] LBH emission excited by both components are obtained, and regions of proton-dominated auroral emission are identified. It is found that the distribution of the ratio of proton-induced to electron-induced brightness resembles maps of the ratio of the respective precipitated energy fluxes. Proton-dominated FUV emissions are thus located in a C-shaped sector extending from prenoon to midnight magnetic local times with a maximum proton contribution near the equatorward boundary of the statistical electron oval. The distribution of the Ly-alpha/LBH intensity ratio is found to mimic the ratio of the proton flux/total energy flux, although it is insufficient by itself to accurately determine the relative fraction of auroral energy carried by the protons. [less ▲]

Detailed reference viewed: 7 (0 ULiège)
See detailElectron and Proton Auroral Dynamics
Mende, S. B.; Frey, H. U.; Carlson, C. et al

Conference (2001, May 01)

Data from the IMAGE Wide-band Imaging Camera (WIC),sensitive to far ultraviolet auroras and from the Spectrographic Imager (SI) channel SI12, sensitive to proton precipitation induced Lyman alpha, were ... [more ▼]

Data from the IMAGE Wide-band Imaging Camera (WIC),sensitive to far ultraviolet auroras and from the Spectrographic Imager (SI) channel SI12, sensitive to proton precipitation induced Lyman alpha, were analyzed during a high altitude orbit segment of the IMAGE spacecraft. This segment began during the expansive phase of a substorm. The aurora developed into a double oval configuration, consisting of a set of discrete poleward forms and a separate diffuse auroral oval equatorwards. Although IMF Bz was negative, considerable activity could be seen poleward of the high latitude arcs in the polar cap region. The optical signature of precipitating protons showed that the proton aurora was on the equatorward side of the diffuse aurora and there was a lack of intense energetic proton fluxes in the poleward arcs. A simultaneous FAST pass provided a diagnostic of the particle types in the various regions. These data showed that lower intensity protons were present throughout the entire double oval configuration but with insufficient intensity to produce aurora that could be observed by IMAGE. The FAST data also showed that the bright poleward discrete arcs were accelerated by electrostatic processes, and the wave accelerated electrons were located on the poleward edge of these features. [less ▲]

Detailed reference viewed: 29 (2 ULiège)
See detailCusp studies with IMAGE-FUV
Frey, H. U.; Mende, S. B.; Fuselier, S. A. et al

Conference (2001, May 01)

The FUV instrument on IMAGE frequently observes localized ultraviolet emission on the high latitude dayside, poleward of the normal auroral oval location. This emission is especially distinct in the ... [more ▼]

The FUV instrument on IMAGE frequently observes localized ultraviolet emission on the high latitude dayside, poleward of the normal auroral oval location. This emission is especially distinct in the observations of Doppler shifted Lyman alpha emission from precipitating protons. We interpret this emission as the optical signature of precipitation into the cusp after lobe reconnection at the magnetopause. Several cusp crossings by the FAST satellite are used to establish an estimate of the energy input and the characteristics of the precipitating protons. Multivariate cluster analysis and other statistical tools are used to determine the dependence of this precipitation on solar wind parameters. This shows that under northward IMF and high solar wind dynamic pressure, proton precipitation can be the dominating energy input into the cusp region. [less ▲]

Detailed reference viewed: 20 (1 ULiège)
See detailDetermination of electron and proton auroral energy inputs from FUV-IMAGE
Gérard, Jean-Claude ULiege; Hubert, Benoît ULiege; Meurant, M. et al

Conference (2001, May 01)

The FUV experiment onboard the IMAGE spacecraft offers the unique possibility to obtain simultaneous snapshots of the global north aurora every 2 minutes in three different spectral channels. The WIC ... [more ▼]

The FUV experiment onboard the IMAGE spacecraft offers the unique possibility to obtain simultaneous snapshots of the global north aurora every 2 minutes in three different spectral channels. The WIC camera has a broadband channel covering the 135-190 nm interval including the N[SUB]2[/SUB] LBH bands, part of which may be absorbed by O[SUB]2[/SUB]. The SI13 channel is centered on the OI 135.6 nm line which is optically thin and includes a ~ 40% LBH contribution. Finally, the SI12 camera images the Doppler-shifted Ly-α emission excited by the proton aurora. This set of instrumentation is combined with auroral models to determine the electron and the proton energy fluxes from the magnetosphere. Examples will be presented and compared with the values deduced from the NOAA satellites. Simultaneous in-situ measurements of the particle characteristic energy have been combined with the data extracted from the FUV images to validate the models and derive empirical relationships between the particle flux measured by the detectors and the brightness observed by FUV-IMAGE at the footprint of the same magnetic field line. Finally, we will assess the ability to deduce the characteristic energy of the auroral particles from the ratio of co-registered images in the WIC and SI13 cameras. This method is based on the difference of vertical distribution of the LBH and the OI 135.6 nm emissions. It offers the potential to globally remotely sense not only the energy flux from the magnetosphere but also the main features of the electron characteristic energy. [less ▲]

Detailed reference viewed: 20 (5 ULiège)
See detailDerivation of Auroral Conductances from IMAGE FUV
Immel, T. J.; Mende, S. B.; Frey, H. U. et al

Conference (2001, May 01)

Auroral emissions are observed in 3 separate Far-Ultraviolet (FUV) wavelength regimes by IMAGE. The Wideband Imaging Camera (WIC) is sensitive mainly to N[SUB]2[/SUB] LBH and N I emissions in the 140-190 ... [more ▼]

Auroral emissions are observed in 3 separate Far-Ultraviolet (FUV) wavelength regimes by IMAGE. The Wideband Imaging Camera (WIC) is sensitive mainly to N[SUB]2[/SUB] LBH and N I emissions in the 140-190-nm range, while the Spectrographic Imager (SI) spectrally separates the OI 135.6-nm emission and Doppler shifted hydrogen emissions of the proton aurora at 121.8 nm. The brightness of the N[SUB]2[/SUB] LBH and OI 135.6-nm emissions depend in part on the spectrum and total energy flux of incoming electrons, and on the height-density profile of the respective species, and O[SUB]2[/SUB]. Due mainly to these atmospheric factors, the ratio of the N[SUB]2[/SUB] and OI emissions depends strongly on the characteristic energy of precipitating electrons which, once estimated, can in turn be used to calculate the total energy flux. The proton aurora generates secondary electrons, which excite additional emissions of N[SUB]2[/SUB] and OI. It is not possible to absolutely determine either the total proton energy flux or the characteristic proton energy (<E[SUB]p[/SUB]>) with a single proton imaging channel. However, the proton-induced N[SUB]2[/SUB] and OI emissions depend mainly on the total proton energy flux, so reasonable estimates of <E[SUB]p[/SUB]> can be used in the calculation of proton energy input. Ground-based or in-situ observations of proton energies can help in this determination. With accurate corrections for N[SUB]2[/SUB] and OI airglow emissions, and formulae such as those provided by Robinson et al. [1987], IMAGE FUV can provide global maps of height-integrated conductivity (conductance) in the auroral oval. It is also possible to examine the degree to which the proton aurora contributes to enhanced conductance on a global scale. The promise of providing these conductances using IMAGE's real-time capabilities will be discussed. Robinson, R. M., R. R. Vondrak, K. Miller, T. Dabbs, and D. Hardy, On Calculating Ionospheric Conductances from the Flux and Energy of Precipitating Electrons, J. Geophys. Res., 92, 2566, 1987. [less ▲]

Detailed reference viewed: 21 (2 ULiège)
Peer Reviewed
See detailThe electron and proton aurora as seen by IMAGE-FUV and FAST
Frey, H. U.; Mende, S. B.; Carlson, C. W. et al

in Geophysical Research Letters (2001), 28

The Far Ultraviolet Instrument (FUV) on the IMAGE spacecraft observes the aurora in three different channels. One of them (SI12) is sensitive to the signal from precipitating protons, while the other two ... [more ▼]

The Far Ultraviolet Instrument (FUV) on the IMAGE spacecraft observes the aurora in three different channels. One of them (SI12) is sensitive to the signal from precipitating protons, while the other two (WIC and SI13) observe 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 with FUV. The measured electron and proton energy spectra are used to calculate the auroral brightness along the FAST orbit. The comparison with the FUV/IMAGE observations shows good quantitative agreement and demonstrates that under certain circumstances high proton fluxes may produce significant amounts of auroral FUV emission. [less ▲]

Detailed reference viewed: 19 (1 ULiège)