Gérard Chanteur - Profile on Academia.edu (original) (raw)
Papers by Gérard Chanteur
Journal of Geophysical Research, Oct 1, 2012
Solitons, oscillitons, and stationary waves in a coldp− α plasma
Journal of Geophysical Research, 2003
We investigate the structure of nonlinear stationary waves propagating transverse and obliquely t... more We investigate the structure of nonlinear stationary waves propagating transverse and obliquely to the magnetic field in a cold plasma consisting of two ion populations, protons and alpha particles. By using the constants of motion which follow from the multifluid equations, the system may be described by a single first‐order differential equation for the transverse case and four coupled first‐order differential equations in the case of oblique propagation. In the transverse case solitons exist if the wave speed lies between the Alfven speed, based on the total mass density, and the Alfven speed modified by the density and charge ratios. At speeds in excess of this latter velocity, periodic solutions exist in which protons and alphas gyrate around each other. An analog of Rankine‐Hugoniot type relations for the amplitude of the solitons and periodic waves is found for structures propagating transverse to the magnetic field. In the case of an oblique stationary wave it is shown that the tip of the proton (alpha ion) flow velocity vector moves on the surface of a sphere whose radius is determined only by the obliquity and the wave speed. Soliton solutions representing both compressions and rarefactions in the ion fluids exist in specific windows in the “Alfven Mach number‐obliquity” space. In other windows, solutions characterized by both oscillating and soliton properties (“oscillitons”) exist. Critical Mach numbers and critical propagation angles limit the size of the windows in which smooth solitons can be constructed.
Current driven weak double layers under linearly stable conditions
The Physics of fluids, Sep 1, 1988
Extensive one-dimensional Vlasov simulations have been performed in order to study the dynamics o... more Extensive one-dimensional Vlasov simulations have been performed in order to study the dynamics of double-layer generation in a stable current carrying plasma. An initial density perturbation, which shortly builds a potential well, leads to a weak double layer and to a recurrent formation of electron vortices for a large range of temperature ratios and electron drift velocities. The electron–vortex formation is inhibited for very small velocity drifts. While the electrostatic energy is generally almost constant, a weak growth develops for an electron drift velocity that is sufficiently high, but less than the critical drift velocity for marginal stability. The amplitude of individual double layers is rather weak, but the collision of two double layers drives a nonlinear instability related to the fusion of electron vortices, amplifying the double-layer potential to several times the electron thermal energy.
Earth, Planets and Space, Feb 1, 2012
HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2010
Annales Geophysicae, Jul 28, 2005
Solar Wind and planetary magnetospheres
Solar Wind interacts with solar system objects by exchanging momentum and energy. This transfer i... more Solar Wind interacts with solar system objects by exchanging momentum and energy. This transfer is particularly effective in the case of weakly magnetized bodies (Mars, Venus and comets) and small magnetosphere (Mercury). This interaction contributes to the erosion of the gaseous envelop and to the atmospheric dynamic and has therefore an important consequence on the atmospheric evolution of these objects. The electromagnetic coupling with these neutral environments takes place through ionization processes: ionization by solar photons, electron impact ionization (incident plasma electrons ionize the upper atmosphere), and charge exchange between ionized and neutral particles producing a cold ion and a fast neutral. At Mars, as the solar wind flow approaches the ionospheric region, more and more of ions originating from the planet are incorporated. This mass loading becomes more important as we approach the object, contributes to the loss of momentum of the flow, and leads to a pile-up and a twist of magnetic field lines around the object, creating an induced magnetosphere. Meanwhile, Mercury has an intrinsic magnetic field that forms a magnetosphere that is to say, a region governed by the ''planetary'' magnetic field and confined by the Solar Wind and IMF. The magnetosphere is also populated by ions with a planetary origin. The main structures of the solar wind plasma interaction with Mars and Mercury can be usually described using a steady state picture; however time-dependent effects play important roles. In the last couple of years we try to address the response of weakly magnetized bodies and small magnetospheres to different time-dependent drivers. Responses of transient events, such IMF rotation or Solar Wind dynamic pressure variation, to induced and intrinsic magnetospheres are compared by means of sophisticated 3D simulations
Investigation of the plasma wake of Titan from RPWS-LP observations and hybrid simulations
ABSTRACT Flybys of Titan by Cassini reveal a highly variable and complex structure of the ionised... more ABSTRACT Flybys of Titan by Cassini reveal a highly variable and complex structure of the ionised environment in the vicinity of Titan. The upstream plasma conditions and the orbital position of Titan, which changes the position of the ionisation sources (photoionisation and electronic impact ionisation), seem to significantly affect the plasma environment around Titan. We focus this study on the analysis of the Titan's plasma wake from the Radio and Plasma Wave Science (RPWS) data, and particularly the Langmuir Probe (LP) observations, and results from three-dimensionnal multi-species hybrid simulations. The electron density and the ion outflow measured by RPWS-LP are compared with hybrid simulation results performed using upstream parameters which are similar to those encountered by Cassini. The simulation model takes into account self-consistently the coupling between the ionised and neutral species. Ionisation of the neutral environment of Titan by solar photons, electron impacts and charge exchange reactions, between the co-rotating plasma and the neutral species, are included in this model. The hybrid model provides a full three-dimensional description of the interaction region and allows to set the observations back to a global context. Few flybys occurred in the wake of Titan, and mainly in the equatorial plane with different geometry encounters, are analyzed for this study.
Journal of Sensors and Sensor Systems, 2013
Electron Parallel Acceleration and Coherent Radiation in the High Altitude Auroral Region. (invited paper)
Planetary and Space Science, 2008
Field-aligned currents and parallel electric field potential drops at Mars. Scaling from the Earth’ aurora
Planetary and Space Science, 2008
Abstract The observations of electron inverted ‘V’ structures by the MGS and MEX spacecraft, thei... more Abstract The observations of electron inverted ‘V’ structures by the MGS and MEX spacecraft, their resemblance to similar events in the auroral regions of the Earth, and the discovery of strong localized magnetic field sources of the crustal origin on Mars, raised hypotheses on the existence of Martian aurora produced by electron acceleration in parallel electric fields. Following the theory of this type of structures on Earth we perform a scaling analysis to the Martian conditions. Similar to the Earth, upward field-aligned currents necessary for the generation of parallel potential drops and peaked electron distributions can arise, for example, on the boundary between ‘closed’ and ‘open’ crustal field lines due to shears of the flow velocity of the magnetosheath or magnetospheric plasmas. A steady-state configuration assumes a closure of these currents in the Martian ionosphere. Due to much smaller magnetic fields as compared to the Earth case, the ionospheric Pedersen conductivity is much higher on Mars and auroral field tubes with parallel potential drops and relatively small cross scales to be adjusted to the scales of the localized crustal patches may appear only if the magnetosphere and ionosphere are decoupled by a zone with a strong E ∥ . Another scenario suggests a periodic short-circuit of the magnetospheric electric fields by a coupling with the conducting ionosphere.
Journal of Geophysical Research: Space Physics, 2008
Simultaneous in situ measurements carried out by the Analyzer of Space Plasma and Energetic Atoms... more Simultaneous in situ measurements carried out by the Analyzer of Space Plasma and Energetic Atoms (ASPERA‐3) and Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instruments on board the Mars Express (MEX) spacecraft for the first time provide us with the local parameters of cold ionospheric and hot solar wind plasma components in the different regions of the Martian magnetosphere and ionosphere. On the dayside, plasma of ionospheric and exospheric origin expands to large altitudes and gets in touch with the solar wind plasma. Formation of the magnetic field barrier which terminates the solar wind flow is governed by solar wind. The magnetic field rises up to the value which is just sufficient to balance the solar wind pressure while the position of the magnetospheric boundary varies insignificantly. Although, within the magnetic barrier, solar wind plasma is depleted, the total electron density increases owing to the enhanced contribution of planetary plasma. In...
IEEE Sensors Journal, 2010
Geophysical Research Letters, 2007
On 26 December 2005, the Cassini spacecraft flew through Titan's plasma wake and revealed a c... more On 26 December 2005, the Cassini spacecraft flew through Titan's plasma wake and revealed a complex and dynamic region. Observations suggest a strong asymmetry which seems to be displaced from the ideal position of the wake. Two distinct plasma regions are identified with a significant difference on the electron number density and on the plasma composition. Simulation results using a three‐dimensional and multi‐species hybrid model, performed in conditions similar to those encountered during the flyby, are presented and compared to the observations. An acceptable agreement is shown between the model predictions and the observations. We suggest that the observed asymmetries, in terms of density and plasma composition, are mainly caused by the a combination of the asymmetry in the ion/electron production rate and the magnetic field morphology, where the first plasma region is connected to the dayside hemisphere of Titan's ionosphere while the other is connected to the nightsid...
Geophysical Research Letters, 2012
Annales Geophysicae, 2003
First Results of the Spatio-Temporal Analysis of Field Fluctuations experiment (STAFF) of Cluster
ABSTRACT STAFF experiment is one of the five experiments which constitute the Cluster Wave Experi... more ABSTRACT STAFF experiment is one of the five experiments which constitute the Cluster Wave Experiment Consortium (WEC). STAFF consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, a wave form unit (up to either 10 Hz or 180 Hz) and a spectrum analyzer (up to 4 kHz) (Cornilleau-Wehrlin et al, 1997). The spectrum analyzer combines the 3 magnetic components of the waves with the two electric components measured by EFW to calculate in real time the 5 5 Hermitian cross-spectral matrix at 27 frequencies distributed logarithmically in the frequency range 8 Hz to 4 kHz. The time resolution varies between 0.125s and 4s. Different tools have been prepared (Cornilleau et al., 2000), specific to the Cluster related studies. The first results presented will show the capabilities of the experiment in different key regions of the magnetosphere-solar wind system encountered by Cluster, using different specific tools.
Advances in Space Research, 2001
Journal of Geophysical Research, Oct 1, 2012
Solitons, oscillitons, and stationary waves in a coldp− α plasma
Journal of Geophysical Research, 2003
We investigate the structure of nonlinear stationary waves propagating transverse and obliquely t... more We investigate the structure of nonlinear stationary waves propagating transverse and obliquely to the magnetic field in a cold plasma consisting of two ion populations, protons and alpha particles. By using the constants of motion which follow from the multifluid equations, the system may be described by a single first‐order differential equation for the transverse case and four coupled first‐order differential equations in the case of oblique propagation. In the transverse case solitons exist if the wave speed lies between the Alfven speed, based on the total mass density, and the Alfven speed modified by the density and charge ratios. At speeds in excess of this latter velocity, periodic solutions exist in which protons and alphas gyrate around each other. An analog of Rankine‐Hugoniot type relations for the amplitude of the solitons and periodic waves is found for structures propagating transverse to the magnetic field. In the case of an oblique stationary wave it is shown that the tip of the proton (alpha ion) flow velocity vector moves on the surface of a sphere whose radius is determined only by the obliquity and the wave speed. Soliton solutions representing both compressions and rarefactions in the ion fluids exist in specific windows in the “Alfven Mach number‐obliquity” space. In other windows, solutions characterized by both oscillating and soliton properties (“oscillitons”) exist. Critical Mach numbers and critical propagation angles limit the size of the windows in which smooth solitons can be constructed.
Current driven weak double layers under linearly stable conditions
The Physics of fluids, Sep 1, 1988
Extensive one-dimensional Vlasov simulations have been performed in order to study the dynamics o... more Extensive one-dimensional Vlasov simulations have been performed in order to study the dynamics of double-layer generation in a stable current carrying plasma. An initial density perturbation, which shortly builds a potential well, leads to a weak double layer and to a recurrent formation of electron vortices for a large range of temperature ratios and electron drift velocities. The electron–vortex formation is inhibited for very small velocity drifts. While the electrostatic energy is generally almost constant, a weak growth develops for an electron drift velocity that is sufficiently high, but less than the critical drift velocity for marginal stability. The amplitude of individual double layers is rather weak, but the collision of two double layers drives a nonlinear instability related to the fusion of electron vortices, amplifying the double-layer potential to several times the electron thermal energy.
Earth, Planets and Space, Feb 1, 2012
HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2010
Annales Geophysicae, Jul 28, 2005
Solar Wind and planetary magnetospheres
Solar Wind interacts with solar system objects by exchanging momentum and energy. This transfer i... more Solar Wind interacts with solar system objects by exchanging momentum and energy. This transfer is particularly effective in the case of weakly magnetized bodies (Mars, Venus and comets) and small magnetosphere (Mercury). This interaction contributes to the erosion of the gaseous envelop and to the atmospheric dynamic and has therefore an important consequence on the atmospheric evolution of these objects. The electromagnetic coupling with these neutral environments takes place through ionization processes: ionization by solar photons, electron impact ionization (incident plasma electrons ionize the upper atmosphere), and charge exchange between ionized and neutral particles producing a cold ion and a fast neutral. At Mars, as the solar wind flow approaches the ionospheric region, more and more of ions originating from the planet are incorporated. This mass loading becomes more important as we approach the object, contributes to the loss of momentum of the flow, and leads to a pile-up and a twist of magnetic field lines around the object, creating an induced magnetosphere. Meanwhile, Mercury has an intrinsic magnetic field that forms a magnetosphere that is to say, a region governed by the ''planetary'' magnetic field and confined by the Solar Wind and IMF. The magnetosphere is also populated by ions with a planetary origin. The main structures of the solar wind plasma interaction with Mars and Mercury can be usually described using a steady state picture; however time-dependent effects play important roles. In the last couple of years we try to address the response of weakly magnetized bodies and small magnetospheres to different time-dependent drivers. Responses of transient events, such IMF rotation or Solar Wind dynamic pressure variation, to induced and intrinsic magnetospheres are compared by means of sophisticated 3D simulations
Investigation of the plasma wake of Titan from RPWS-LP observations and hybrid simulations
ABSTRACT Flybys of Titan by Cassini reveal a highly variable and complex structure of the ionised... more ABSTRACT Flybys of Titan by Cassini reveal a highly variable and complex structure of the ionised environment in the vicinity of Titan. The upstream plasma conditions and the orbital position of Titan, which changes the position of the ionisation sources (photoionisation and electronic impact ionisation), seem to significantly affect the plasma environment around Titan. We focus this study on the analysis of the Titan's plasma wake from the Radio and Plasma Wave Science (RPWS) data, and particularly the Langmuir Probe (LP) observations, and results from three-dimensionnal multi-species hybrid simulations. The electron density and the ion outflow measured by RPWS-LP are compared with hybrid simulation results performed using upstream parameters which are similar to those encountered by Cassini. The simulation model takes into account self-consistently the coupling between the ionised and neutral species. Ionisation of the neutral environment of Titan by solar photons, electron impacts and charge exchange reactions, between the co-rotating plasma and the neutral species, are included in this model. The hybrid model provides a full three-dimensional description of the interaction region and allows to set the observations back to a global context. Few flybys occurred in the wake of Titan, and mainly in the equatorial plane with different geometry encounters, are analyzed for this study.
Journal of Sensors and Sensor Systems, 2013
Electron Parallel Acceleration and Coherent Radiation in the High Altitude Auroral Region. (invited paper)
Planetary and Space Science, 2008
Field-aligned currents and parallel electric field potential drops at Mars. Scaling from the Earth’ aurora
Planetary and Space Science, 2008
Abstract The observations of electron inverted ‘V’ structures by the MGS and MEX spacecraft, thei... more Abstract The observations of electron inverted ‘V’ structures by the MGS and MEX spacecraft, their resemblance to similar events in the auroral regions of the Earth, and the discovery of strong localized magnetic field sources of the crustal origin on Mars, raised hypotheses on the existence of Martian aurora produced by electron acceleration in parallel electric fields. Following the theory of this type of structures on Earth we perform a scaling analysis to the Martian conditions. Similar to the Earth, upward field-aligned currents necessary for the generation of parallel potential drops and peaked electron distributions can arise, for example, on the boundary between ‘closed’ and ‘open’ crustal field lines due to shears of the flow velocity of the magnetosheath or magnetospheric plasmas. A steady-state configuration assumes a closure of these currents in the Martian ionosphere. Due to much smaller magnetic fields as compared to the Earth case, the ionospheric Pedersen conductivity is much higher on Mars and auroral field tubes with parallel potential drops and relatively small cross scales to be adjusted to the scales of the localized crustal patches may appear only if the magnetosphere and ionosphere are decoupled by a zone with a strong E ∥ . Another scenario suggests a periodic short-circuit of the magnetospheric electric fields by a coupling with the conducting ionosphere.
Journal of Geophysical Research: Space Physics, 2008
Simultaneous in situ measurements carried out by the Analyzer of Space Plasma and Energetic Atoms... more Simultaneous in situ measurements carried out by the Analyzer of Space Plasma and Energetic Atoms (ASPERA‐3) and Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instruments on board the Mars Express (MEX) spacecraft for the first time provide us with the local parameters of cold ionospheric and hot solar wind plasma components in the different regions of the Martian magnetosphere and ionosphere. On the dayside, plasma of ionospheric and exospheric origin expands to large altitudes and gets in touch with the solar wind plasma. Formation of the magnetic field barrier which terminates the solar wind flow is governed by solar wind. The magnetic field rises up to the value which is just sufficient to balance the solar wind pressure while the position of the magnetospheric boundary varies insignificantly. Although, within the magnetic barrier, solar wind plasma is depleted, the total electron density increases owing to the enhanced contribution of planetary plasma. In...
IEEE Sensors Journal, 2010
Geophysical Research Letters, 2007
On 26 December 2005, the Cassini spacecraft flew through Titan's plasma wake and revealed a c... more On 26 December 2005, the Cassini spacecraft flew through Titan's plasma wake and revealed a complex and dynamic region. Observations suggest a strong asymmetry which seems to be displaced from the ideal position of the wake. Two distinct plasma regions are identified with a significant difference on the electron number density and on the plasma composition. Simulation results using a three‐dimensional and multi‐species hybrid model, performed in conditions similar to those encountered during the flyby, are presented and compared to the observations. An acceptable agreement is shown between the model predictions and the observations. We suggest that the observed asymmetries, in terms of density and plasma composition, are mainly caused by the a combination of the asymmetry in the ion/electron production rate and the magnetic field morphology, where the first plasma region is connected to the dayside hemisphere of Titan's ionosphere while the other is connected to the nightsid...
Geophysical Research Letters, 2012
Annales Geophysicae, 2003
First Results of the Spatio-Temporal Analysis of Field Fluctuations experiment (STAFF) of Cluster
ABSTRACT STAFF experiment is one of the five experiments which constitute the Cluster Wave Experi... more ABSTRACT STAFF experiment is one of the five experiments which constitute the Cluster Wave Experiment Consortium (WEC). STAFF consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, a wave form unit (up to either 10 Hz or 180 Hz) and a spectrum analyzer (up to 4 kHz) (Cornilleau-Wehrlin et al, 1997). The spectrum analyzer combines the 3 magnetic components of the waves with the two electric components measured by EFW to calculate in real time the 5 5 Hermitian cross-spectral matrix at 27 frequencies distributed logarithmically in the frequency range 8 Hz to 4 kHz. The time resolution varies between 0.125s and 4s. Different tools have been prepared (Cornilleau et al., 2000), specific to the Cluster related studies. The first results presented will show the capabilities of the experiment in different key regions of the magnetosphere-solar wind system encountered by Cluster, using different specific tools.
Advances in Space Research, 2001