Electron and proton excitation of the FUV aurora: Simultaneous IMAGE and NOAA observations

Coumans, Valérie; Gérard, Jean‐Claude; Hubert, Benoît; Evans, David S.

doi:10.1029/2001ja009233

Cited by 37 publications

(70 citation statements)

References 27 publications

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“…The comparison was made for both WIC and SI12 data. Taking into consideration all possible sources of error, WIC observations showed agreement with in situ induced auroral brightness within 70%, but SI12 observations coupled with simulation from the Monte Carlo code predicted proton fluxes twice as large as the in situ measurements (Coumans et al, 2002). Consequently, in this work, the proton energy fluxes are adjusted by a factor of 2 to account for this overestimate of the SI12 derived proton flux.…”

Section: The Fuv Imagers and The Auroral Precipitationmentioning

confidence: 99%

“…This discrepancy was tentatively attributed to highenergy protons above the 30 keV upper limit of the detectors, suggesting that higher energy protons could be important in producing this emission. Coumans et al (2002) used in situ particle measurements from NOAA-15 and NOAA-16 satellites to check this possibility and assess the role of proton excitation of FUV emissions. The NOAA sets of detectors offers the advantage of observing electrons in the energy range 50 eV-1000 keV and protons from 50 eV to 800 keV, including all relevant auroral energies.…”

Section: The Fuv Imagers and The Auroral Precipitationmentioning

confidence: 99%

“…However, several studies (Basu et al, 1987;Galand et al, 1999;Coumans et al, 2002) have shown that protons play a major role on the ionospheric densities at given locations and times. Recently, Galand et al (2001a) proposed a simple way to parameterize the Pedersen and Hall conductances due to auroral proton precipitation and applied them to the Hardy et al (1989) statistical patterns of precipitating proton flux and mean energy (Galand et al, 2001b).…”

Section: Introductionmentioning

confidence: 99%

“…The imagers are designed to monitor the electron and proton precipitation and discriminate between the two types of particles. Previous studies have shown the quantitative and qualitative validity of FUV instruments from comparisons with in situ auroral particle measurements Gérard et al, 2001;Coumans et al, 2002). Section 2 briefly describes the method used to extract the particle energy and energy flux characteristics from the FUV observations.…”

Section: Introductionmentioning

confidence: 99%

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Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

et al. 2004

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Abstract. The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI12 camera sensitive to Doppler shifted Lyman-α emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI12 around 14:00 MLT at ∼75 • MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in auroral arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop along field lines in the upward field-aligned currents by creating an opposite polarization electric field. This feedback mechanism possibly reduces the electron acceleration.

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Section: The Fuv Imagers and The Auroral Precipitationmentioning

confidence: 99%

Section: The Fuv Imagers and The Auroral Precipitationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

et al. 2004

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“…Comparison with the Ly-α emission extracted along the satellite track from SI12 images showed good agreement with the peak value at the center of the proton arc , although the latitudinally integrated brightness may underestimate the observations by up to a factor of 2. 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, particularly in the afternoon sector.…”

Section: Introductionmentioning

confidence: 99%

Remote sensing of the proton aurora characteristics from IMAGE-FUV

Бисикало

Shematovich

Gérard³

et al. 2003

Ann. Geophys.

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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-α 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 protondominated 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.

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Comparative study of large‐scale auroral signatures of substorms, steady magnetospheric convection events, and sawtooth events

et al. 2017

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This paper investigates the auroral evolution during different magnetospheric modes: substorms, steady magnetospheric convection, and sawtooth events. We undertake a superposed epoch analysis using data from the Imager for Magnetopause‐to‐Aurora Global Exploration Far Ultraviolet spectrographic imager and wideband imaging camera for each of these event types. We find that the auroral oval narrows and shows an equatorward movement prior to substorm onset. At substorm onset, the auroral oval brightens explosively near 23 magnetic local time (MLT). After this the aurorae expand poleward and the brightening stretches duskward and dawnward, with the duskward expansion being faster. Approximately 20 min after substorm onset, the aurorae begin to dim. Steady magnetospheric convection events with preceding substorms initially show the same signatures as substorms, but instead of the recovery after 20 min postonset, the aurorae stay bright for an extended period of time (at least 4 h after onset). Despite continued dayside driving of the system during steady magnetospheric convection events, we see a reconfiguration in the nightside auroral activity, taking place between 120 to 150 min after onset. Sawtooth events show very similar signatures to substorms, except for the auroral emission being much brighter, covering a wider MLT extent, and taking significantly less time to recover. The proton aurorae during substorms take ∼2–4 h to dim, during sawtooth events this process takes less than 1 h, despite enhanced reconnection rates. A similar effect is seen in the electron aurorae, albeit not as extreme.

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Electron and proton excitation of the FUV aurora: Simultaneous IMAGE and NOAA observations

Cited by 37 publications

References 27 publications

Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

Remote sensing of the proton aurora characteristics from IMAGE-FUV

Comparative study of large‐scale auroral signatures of substorms, steady magnetospheric convection events, and sawtooth events

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