References of "Grodent, Denis"
     in
Bookmark and Share    
See detailAuroral counterpart of magnetic field dipolarizations in Saturn's tail
Jackman, C. M.; Achilleos, N.; Bunce, E. J. et al

in American Geophysical Union, Fall Meeting 2011, abstract #SM14A-07 (2011, December 01)

Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations ... [more ▼]

Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations can be initially identified from the magnetometer data by looking for a southward turning of the magnetic field, indicating the transition from a radially stretched configuration to a more dipolar field topology. The highly stretched geometry of the kronian magnetotail lobes gives rise to a tail current which flows eastward (dusk to dawn) in the near equatorial plane across the centre of the tail. During reconnection and associated dipolarization of the field, the inner edge of this tail current can be diverted through the ionosphere, in a situation analogous to the substorm current wedge picture at Earth [McPherron et al. 1973]. We present a picture of the current circuit arising from this tail reconfiguration, and outline the equations which govern the field-current relationship. We show a number of examples of dipolarizations as identified in the Cassini magnetometer data and use this formalism to calculate limits for the ionospheric current density that would arise for these examples. In addition to the magnetometer data, we also present data from the Cassini VIMS and UVIS instruments which have observed small 'spots' of auroral emission lying near the main oval - features thought to be associated with dipolarizations in the tail. We compare the auroral intensities as predicted from our calculation with the observed spot sizes and intensities. [less ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
See detailOn the origin of the 2-3 minutes quasi-periodicity in the Jovian magnetosphere
Bonfond, Bertrand ULg; Vogt, Marissa F.; Gérard, Jean-Claude ULg et al

Poster (2011, October 05)

Several kinds of periodicities have been observed at Jupiter since the first probes fly-by. However, pre- vious investigations mainly focused on the longer timescales, such as the 40 minutes (QP40) or the ... [more ▼]

Several kinds of periodicities have been observed at Jupiter since the first probes fly-by. However, pre- vious investigations mainly focused on the longer timescales, such as the 40 minutes (QP40) or the 2- 3 days quasi-periodicity. Here we describe the recent finding of the 2-3 minutes quasi-periodic occurrence of UV flares in the active region of the polar aurora. These observations are then compared to other measurements of such quasi-periodic behaviors in electron and magnetic field data and their probably common origin is discussed. [less ▲]

Detailed reference viewed: 25 (12 ULg)
Full Text
See detailThe energy the auroral electrons in Saturn's atmosphere : remote sensing and thermal consequences
Gérard, Jean-Claude ULg; Gustin, Jacques ULg; Grodent, Denis ULg et al

Poster (2011, October)

Saturn’s north aurora has been observed between January and May 2011 with the Hubble Space Telescope. The objective was to collect spatially resolved spectra at the different local time from dawn to dusk ... [more ▼]

Saturn’s north aurora has been observed between January and May 2011 with the Hubble Space Telescope. The objective was to collect spatially resolved spectra at the different local time from dawn to dusk and compare them with laboratory or synthetic spectra. For this purpose, HST was programmed to slew from mid-latitudes through the auroral oval up to above the limb while collecting data in the timetag mode. The spectra show signatures of absorption by hydrocarbons present above the peak of the auroral emission. The amount of absorption and implications in terms of penetration of the auroral electron beam into Saturn’s atmosphere will be discussed and compared with other determinations of the altitude of the aurora. The effects of the auroral heat import on the thermal structure of the atmosphere both at high and low altitudes will be examined in the light of these results. [less ▲]

Detailed reference viewed: 15 (5 ULg)
Full Text
See detailModel of the Jovian magnetic field topology constrained by the Io auroral emissions
Hess, Sébastien; Bonfond, Bertrand ULg; Grodent, Denis ULg et al

Poster (2011, October)

The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some ... [more ▼]

The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins along Io’s orbit. The use of this latter constraint to determine the internal magnetic field models greatly improved the modeling of the auroral emissions, in particular the radio ones, which strongly depends on the magnetic field geometry. This constraint is, however, not sufficient for allowing a completely accurate modeling. The fact that the footprint field line should map to a longitude close to Io’s was not used, so that the azimuthal component of the magnetic field could not be precisely constrained. Moreover, a recent study showed the presence of a magnetic anomaly in the northern hemisphere, which has never been included in any spherical harmonic decomposition of the internal magnetic field. We compute a decomposition of the Jovian internal magnetic field into spherical harmonics, which allows for a more accurate mapping of the magnetic field lines crossing Io, Europa, and Ganymede orbits to the satellite footprints observed in UV. This model, named VIPAL, is mostly constrained by the Io footprint positions, including the longitudinal constraint, and normalized by the Voyager and Pioneer magnetic field measurements. We show that the surface magnetic fields predicted by our model are more consistent with the observed frequencies of the Jovian radio emissions than those predicted by previous models. [less ▲]

Detailed reference viewed: 28 (13 ULg)
Full Text
See detailBi-directional electron distributions as tracers for the open-closed field line boundary in Saturn’s magnetosphere
Krupp, Norbert; Radioti, Aikaterini ULg; Roussos, Elias et al

Conference (2011, October)

In this presentation we use bi-directional energetic electron distributions from the MIMI-LEMMS instrument onboard Cassini, auroral observations from the Hubble Space Telescope (HST) and data from the ... [more ▼]

In this presentation we use bi-directional energetic electron distributions from the MIMI-LEMMS instrument onboard Cassini, auroral observations from the Hubble Space Telescope (HST) and data from the UVIS instrument onboard Cassini to characterize the open-closed field line boundary in Saturn’s magnetosphere. The high-latitude open-closed field line boundary at Saturn is thought to be related to the main auroral ring of emission of the planet varying in location, intensity and latitudinal extent as well as in its homogeneity. This study extends the work on the plasmapause/open-closed field line boundary published by [1] by covering a larger data set at different local times and comparing the electron distributions with auroral observations. Based on energetic electron data we characterize the open-closed field line boundary in terms of temporal, local time variations and other parameters and we correlate the Cassini in-situ measurements to the observations of the main auroral ring at Saturn. [less ▲]

Detailed reference viewed: 11 (1 ULg)
Full Text
See detailDetection of Auroral Emissions from Callisto’s Magnetic Footprint at Jupiter
Clarke, J. T.; Wannawichian, S.; Hernandez, N. et al

Poster (2011, October)

HST observations of Jupiter’s aurora in a large campaign reveal several cases where the main oval emission appeared at unusually low latitudes, making it possible to search for the first time for auroral ... [more ▼]

HST observations of Jupiter’s aurora in a large campaign reveal several cases where the main oval emission appeared at unusually low latitudes, making it possible to search for the first time for auroral emissions from the magnetic footprint of Callisto without the overlapping bright emissions from the main oval. Several cases have been found where point-source emissions have now been detected from locations consistent with Callisto’s magnetic footprint on Jupiter at a brightness of ten’s of kilo- Rayleighs. These observations confirm that there is an electrodynamic interaction between Callisto and Jupiter’s magnetospheric environment that is similar to those at Io, Europa, and Ganymede, which all have auroral footprints. The properties of the emissions and a comparison with other observations and theoretical expectations will be presented in this paper. [less ▲]

Detailed reference viewed: 20 (3 ULg)
Full Text
See detailUV and visible planetary auroral emissions: Jupiter and Saturn
Grodent, Denis ULg

Conference (2011, October)

In the giant planets upper atmosphere, collisions of auroral electrons with atmospheric H atoms and H2 molecules, following acceleration along magnetic field lines, give rise to excitation of these ... [more ▼]

In the giant planets upper atmosphere, collisions of auroral electrons with atmospheric H atoms and H2 molecules, following acceleration along magnetic field lines, give rise to excitation of these primary neutrals. Excited H and H2 almost immediately loose part of (~15%) their excess energy through radiative decay processes implying emission of FUV, EUV, NUV and visible light. An observer located near Earth orbit will only see the sunlit portion of the giant planets for which the reflected sunlight outshines a large portion of the hydrogen auroral emissions. Fortunately, the solar spectrum drops by several orders of magnitude in the FUV-EUV bandpass and is further attenuated by low altitude hydrocarbon haze produced in the polar regions. This makes it possible to observe Jupiter and Saturn EUV and FUV auroras from Earth orbit with, for example, the UV cameras onboard the Hubble Space Telescope. These cameras provided numerous fantastic views of Jupiter and Saturn's polar auroral emissions. By contrast, the dimmer NUV and visible auroral emissions cannot compete with the solar light and can only be observed on the night side hemisphere of Jupiter and Saturn; out of visibility from Earth orbit. This region is accessible to in situ spacecraft, like Galileo, Cassini or NewHorizons, which have to share their precious observing time among several different scientific topics. As a result, images of the NUV and visible auroral emissions are rare, in comparison with the huge HST database. Nevertheless, the fact that they are only captured in the night side implies that the origin of the energetic particles that gave rise to them is principally found in the immense magnetospheric tail; a vast region where energetic electromagnetic processes and plasma motions are still poorly documented. This makes these emissions invaluable in terms of scientific return. [less ▲]

Detailed reference viewed: 14 (1 ULg)
See detailJUDE: A Far-UV Imager for JUICE
Grodent, Denis ULg; Bunce, Emma; Bannister, Nigel et al

Poster (2011, August 31)

Detailed reference viewed: 38 (5 ULg)
See detailUV-IR comparison: Jupiter aurora
Gérard, Jean-Claude ULg; Grodent, Denis ULg

Conference (2011, August)

Detailed reference viewed: 16 (1 ULg)
See detailThe Ultraviolet Spectrograph (UVS) on Juno
Gladstone, G. R.; Persyn, S.; Eterno, J. et al

Poster (2011, July 11)

Detailed reference viewed: 32 (5 ULg)
See detailCassini UVIS Observations of Varying Auroral Emissions on Saturn's Night Side
Pryor, W.; Esposito, L.; Jouchoux, A. et al

Poster (2011, July 11)

Detailed reference viewed: 11 (3 ULg)
See detailAuroral signatures of injections in the magnetosphere of Saturn
Radioti, Aikaterini ULg; Roussos, E.; Grodent, Denis ULg et al

Poster (2011, July 11)

Detailed reference viewed: 22 (12 ULg)
See detailMapping Jupiter's auroral features to magnetospheric sources: Comparing results from three different models for Jupiter's ionospheric magnetic field
Vogt, M. F.; Kivelson, M. G.; Khurana, K. K. et al

Conference (2011, July 11)

Detailed reference viewed: 11 (1 ULg)
See detailInside the Jupiter Main Auroral Emissions: Flares, Spots, Arc...and Satellite Footprints?
Bonfond, Bertrand ULg; Vogt, M. F.; Yoneda, M. et al

Conference (2011, July 11)

Detailed reference viewed: 22 (11 ULg)
See detailThe multiple spots of the Ganymede footprint
Bonfond, Bertrand ULg; Hess, S.; Grodent, Denis ULg et al

Poster (2011, July 11)

Detailed reference viewed: 15 (7 ULg)
See detailModel of the Jovian magnetic field topology constrained by the Io auroral emissions
Hess, S.; Bonfond, Bertrand ULg; Grodent, Denis ULg et al

Poster (2011, July 11)

Detailed reference viewed: 3 (1 ULg)
See detailAuroral emissions of Europa
Grodent, Denis ULg

Conference (2011, June 01)

Detailed reference viewed: 8 (1 ULg)