References of "Coumans, Valérie"
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See detailHigh-Resolution Limb Observations of Proton Aurora
Chua, D. H.; Dymond, K. F.; Budzien, S. A. et al

Conference (2003, December 01)

The interaction of precipitating protons in the upper atmosphere involves charge exchange, ionization, elastic and inelastic collisions, and the deposition of energy from the bottom of the F-region to the ... [more ▼]

The interaction of precipitating protons in the upper atmosphere involves charge exchange, ionization, elastic and inelastic collisions, and the deposition of energy from the bottom of the F-region to the D-region of the ionosphere. These processes and the transport of incident protons through this range of altitudes has been described through a variety of modeling techniques but there has been a dearth of altitude-resolved observations of proton precipitation with which to validate such models. We present new limb observations of Doppler-shifted Lyman-α proton aurora emissions obtained by the High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS) that fill this niche. HITS performs limb scans that include tangent altitudes between 90 km and 400 km with approximately 5 km vertical resolution. The Doppler shifts of the proton aurora Lyman-α emissions are measured with 1.5 Angstrom resolution and are used to infer mean energies of the incident protons as a function of altitude. Observed energy-range (dE/dz) relations are compared to those predicted by a Monte Carlo simulation of proton transport in the upper atmosphere. [less ▲]

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See detailDynamics of global scale electron and proton precipitation induced by a solar wind pressure pulse
Meurant, M.; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in Geophysical Research Letters (2003), 30(20),

[1] On April 28 2001, simultaneous global images of electron and proton aurora were obtained by IMAGE- FUV following a sudden increase of solar wind dynamic pressure. The local time and intensity ... [more ▼]

[1] On April 28 2001, simultaneous global images of electron and proton aurora were obtained by IMAGE- FUV following a sudden increase of solar wind dynamic pressure. The local time and intensity distribution of both types of precipitation are examined and compared. It is found that the electron and the proton precipitation both start in the post noon sector and expand concurrently, but the expansion into the nightside starts sooner for the protons than for the electrons. The characteristic rise time in the onset sector is on the order of 6 minutes. A distinct dynamics and morphology of electron and proton precipitation is observed in the nightside sector. DMSP electron measurements in the afternoon sector indicate that the shock has a significant effect on the electron spectral characteristics. It is suggested that the various Alfven frequencies generated by the shock account for the two different speeds of propagation of the disturbance. [less ▲]

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See detailHigh resolution FUV observations of proton aurora
Chua, D. H.; Dymond, K. F.; Budzien, S. A. et al

in Geophysical Research Letters (2003), 30(18),

We present new FUV observations of Doppler-shifted Lyman-alpha emissions from proton aurora obtained from the High Resolution Ionospheric and Thermospheric Spectrograph ( HITS) aboard the Advanced ... [more ▼]

We present new FUV observations of Doppler-shifted Lyman-alpha emissions from proton aurora obtained from the High Resolution Ionospheric and Thermospheric Spectrograph ( HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS). The HITS instrument observes the Doppler-shifted H Lyman-alpha emissions from proton precipitation with 1.5 Angstrom resolution. The high spectral resolution of these measurements allows the auroral Lyman-alpha emissions to be separated from the intense geocoronal background. The measured proton aurora Doppler spectra are modeled using a Monte Carlo simulation of proton flux transport. The forward modeling performed with this code allows us to infer the characteristic energies of the incident protons from the measured Lyman-alpha Doppler spectra. The inferred characteristics of dayside versus nightside proton precipitation are compared and used to identify the magnetospheric regions from which the particles likely originated. [less ▲]

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See detailCharacterization and dynamics of the auroral electron precipitation during substorms deduced from IMAGE-FUV
Meurant, M.; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in Journal of Geophysical Research. Space Physics (2003), 108(A6),

[1] The FUV imager on board the IMAGE satellite provides simultaneous images of the north polar aurora every 2 min in three spectral channels. The Wideband Imaging Camera (WIC) responds primarily to the N ... [more ▼]

[1] The FUV imager on board the IMAGE satellite provides simultaneous images of the north polar aurora every 2 min in three spectral channels. The Wideband Imaging Camera (WIC) responds primarily to the N-2 LBH bands while one of the Spectral Imagers (SI13) includes the OI 135.6 nm emission and nearby LBH bands. The third channel (SI12) is sensitive to Doppler-shifted Lyman-alpha emission at 121.8 nm generated by proton precipitation. The relative magnitude of the WIC and SI13 signals depends on the altitude distribution of the energy deposition, in response to the differential O-2 absorption and the altitude dependence of the neutral composition. The ratio of simultaneous images from WIC and SI13 is used to derive the spatial distribution of the characteristic energy of the precipitating auroral electrons and the energy flux they carry. The method is described and the uncertainties introduced by possible perturbations of the neutral composition known to occur in the auroral thermosphere are discussed. The first part of this study describes a validation of this method performed by comparing precipitation characteristics derived from FUV with in situ measurements from two coincident passes of the NOAA-16 satellite. They are shown to agree within about 45%. The second part applies this ratio method to analyze the time evolution of auroral activity which occured during two substorms on 28 October 2000. The time evolution is displayed in the form of magnetic local time and magnetic latitude keograms. It is shown that the pattern of the electron average energy distribution exhibits both spatial and temporal changes. Comparison with FAST in situ electron spectrograms confirms the ability of IMAGE to detect precipitation events with a similar to200 km spatial scale. However the characteristics of the physical process leading to electron acceleration cannot be identified with FUV. The highest values of the average energy are colocated in time and space with the largest electron precipitation fluxes. A dawnward motion of bright features is observed in the postmidnight at speeds on the order of 5 magnetic local time hours/UT hour. [less ▲]

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See detailElectron and proton shock aurora observed by IMAGE-FUV
Meurant, M.; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in EGS - AGU - EUG Joint Assembly (2003, April 01)

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

The FUV instrument on the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite monitors the aurora in three different spectral regions. The Wideband Imaging Camera (WIC) observes the molecular N_2 LBH and the atomic NI emissions at 140-180 nm. The two channels of the Spectrographic Imager (SI) observe the Doppler shifted Lyman-α emission at 121.8 nm due to precipitating protons (SI12) and the electron auroral emission of OI at 135.6 nm (SI13). Three simultaneous snapshots are recorded each 2 minutes. In this study, the FUV instrument allows a global viewing of the aurora with a high temporal resolution both in proton and electron. It is used to study the shock aurora resulting from the disturbance caused by the arrival of a coronal mass ejection on the front of the magnetosphere. A comparison between electron and proton injection features at global scale is performed for different isolated events with positive and negative interplanetary B_z. A correlation with IMF and solar wind parameters is presented as well as a description of the magnetosphere morphology given by the Tsyganenko model in the shock aurora period. [less ▲]

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See detailElectron and proton shock aurora observed by IMAGE-FUV
Meurant, M.; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in EGS - AGU - EUG Joint Assembly (2003, April 01)

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

The FUV instrument on the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite monitors the aurora in three different spectral regions. The Wideband Imaging Camera (WIC) observes the molecular N_2 LBH and the atomic NI emissions at 140-180 nm. The two channels of the Spectrographic Imager (SI) observe the Doppler shifted Lyman-α emission at 121.8 nm due to precipitating protons (SI12) and the electron auroral emission of OI at 135.6 nm (SI13). Three simultaneous snapshots are recorded each 2 minutes. In this study, the FUV instrument allows a global viewing of the aurora with a high temporal resolution both in proton and electron. It is used to study the shock aurora resulting from the disturbance caused by the arrival of a coronal mass ejection on the front of the magnetosphere. A comparison between electron and proton injection features at global scale is performed for different isolated events with positive and negative interplanetary B_z. A correlation with IMF and solar wind parameters is presented as well as a description of the magnetosphere morphology given by the Tsyganenko model in the shock aurora period. [less ▲]

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See detailSeasonal effects on the proton auroral precipitation observed by IMAGE-FUV
Coumans, Valérie ULg; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in EGS - AGU - EUG Joint Assembly (2003, April 01)

The statistical approach of the auroral electron precipitation has shown a summer/winter dissymmetry. Electron energy flux in the 1900-0300 MLT sector increases from summer to winter. The frequency of ... [more ▼]

The statistical approach of the auroral electron precipitation has shown a summer/winter dissymmetry. Electron energy flux in the 1900-0300 MLT sector increases from summer to winter. The frequency of occurrence of intense aurora (with electron energy flux above 5 erg cm[SUP]-2[/SUP] s[SUP]-1[/SUP]) in the dusk-to-midnight sector was observed to be 3 times higher under winter conditions (or conditions of local darkness) than under summer conditions (or in sunlight). On board the IMAGE satellite the FUV instruments monitor the aurora in three different spectral regions and especially one of them only images the auroral proton precipitation. The Wideband Imaging Camera (WIC) observes the molecular N_2 LBH and the atomic NI emissions between 140 and 180 nm. The two channels of the Spectrographic Imager (SI) respond to the Doppler shifted Lyman-α emission at 121.8 nm due to precipitating protons (SI12) and the electron auroral emission of OI at 135.6 nm (SI13). The auroral proton and electron energy fluxes are calculated from the IMAGE-FUV data, relying on energy degradation and auroral emission models. We will discuss possible seasonal asymmetry in the auroral proton precipitation. A statistical study is made with FUV data from 2 successive solstices to minimize effects due to the solar activity variations. [less ▲]

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See detailElectron and proton excitation of the FUV aurora: Simultaneous IMAGE and NOAA observations
Coumans, Valérie ULg; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in Journal of Geophysical Research. Space Physics (2002), 107

The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite provides a global view of the north auroral region in different spectral channels. The Wideband Imaging Camera (WIC) is sensitive to ... [more ▼]

The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite provides a global view of the north auroral region in different spectral channels. The Wideband Imaging Camera (WIC) is sensitive to the N[SUB]2[/SUB] LBH emission and NI emissions produced by both electron and proton precipitations. The SI12 camera images the Lyman-alpha emission due to incident protons only. We compare WIC and SI12 observations with model predictions based on particle measurements from the TED and the MEPED detectors on board NOAA-TIROS spacecraft. Models of the interaction of auroral particles with the atmosphere are used together with the in situ proton and electron flux and characteristic energy data to calculate the auroral brightness at the magnetic footprint of the NOAA-15 and NOAA-16 orbital tracks. The MEPED experiment measures the precipitating particles with energy higher than 30 keV, so that these comparisons include all auroral energies, in contrast to previous comparisons. A satisfactory agreement in morphology and in magnitude is obtained for most satellite overflights. The observed FUV-WIC signal is well modeled if the different spatial resolution of the two sensors is considered and the in situ measurements properly smoothed. The calculated count rate includes contributions from LBH emission, the NI 149.3 nm line, and the OI 135.6 nm line excited by electrons and protons. The proton contribution in WIC can locally dominate the electrons. The comparisons indicate that protons can significantly contribute to the FUV aurora at specific times and places and cannot be systematically neglected. The results confirm the shift of the proton auroral oval equatorward of the electron oval in the dusk sector. We also show that in some regions, especially in the dusk sector, high-energy protons dominate the proton energy flux and account for a large fraction of the Lyman-alpha and other FUV emissions. [less ▲]

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See detailIMAGE-FUV multispectral observation of theta auroras.
Hubert, Benoît ULg; Gérard, Jean-Claude ULg; Mende, S. B. et al

Conference (2002, May 01)

The theta aurora is an auroral structure presenting a sun-aligned transpolar arc. Five different dynamic evolution of the transpolar arcs are known, some of them being symmetrical to each other, leaving ... [more ▼]

The theta aurora is an auroral structure presenting a sun-aligned transpolar arc. Five different dynamic evolution of the transpolar arcs are known, some of them being symmetrical to each other, leaving three basically different types of transpolar auroral features. The theta aurora was previously studied with in-situ particles detectors onboard polar orbiting satellites and by ultraviolet imagers. Previous imaging works focused on the electron aurora. We use the FUV imagers onboard the IMAGE spacecraft to study separately the proton and electron contributions to the transpolar arcs at the global scale. The imagers of the IMAGE-FUV experiment remotely sense the electron aurora with the WIC and SI13 imagers observing respectively the N[SUB]2[/SUB]-LBH and OI-135.6 nm emission, while the SI12 spectrographic imager measures the Doppler-shifted Lyman-ë± emission which is solely due to the auroral proton precipitation. The three different types of transpolar aurora will be analyzed using the IMAGE-FUV imagers. In particular, the relative contribution of proton and electron to the excitation of the theta aurora will be presented. [less ▲]

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See detailIonospheric Conductances Due To Auroral Proton and Electron Precipitation Deduced From Image-fuv Observations.
Coumans, Valérie ULg; Hubert, Benoît ULg; 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 ▲]

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