mission demeter quelques résultats sur lionosphère j.j. berthelier, t. onishi, x. wang*, e. seran...
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Mission DEMETERQuelques résultats sur l’ionosphère
J.J. Berthelier, T. Onishi, X. Wang*, E. Seran (LATMOS), M. Malingre (LPP)* Maintenant à OCA
Atelier Pôle Système Solaire IPSL, Avril 2013
Plan
1- DEMETER: objectifs et charge utile scientifiques
2- Recherche d’effets pré-sismiques
3- Perturbations induites par les émetteurs VLF
4- Effets d’une éclipse dans l’ionosphère supérieure
5- Perturbations ionosphériques associées aux ondes de gravité
6- Instabilités de l’ionosphère équatoriale
DEMETER
DEMETERMission et Objectifs Scientifiques
- Premier µ-satellite de la famille MYRIADES du CNES
- Lancement depuis Baïkonour le 29 juin 2004 par lanceur Dniepr (ex SS19)
- Arrêt des opérations 9 décembre 2010- Plus de 6 ans de bons et loyaux services
Objectifs scientifiques de la mission
1- Recherche d’effets ionosphériques pré-sismiques
2- Perturbations ionosphériques induites par les activités humaines
3- Physique de l’ionosphère et météorologie spatiale
DEMETER
Orbit- Circular at 715 km (later 650 km) , 98° inclination, - Quasi helio-synchronous
- nodes ascending ~ 22.30 LT, descending ~ 10.30 LT- 3 axis stabilized, X nadir, - Z aligned with orbital velocity
DEMETEROrbites et zones de mode Burst
DEMETERRecherche d’effets pré-sismiques dans l’ionosphère
Analyse statistiques des ondes VLF
M ≥ 4.8, d ≤40 km
Distribution statistiqueSans activité sismique
M>5, d ≤40 km M>5, d ≤40 km
DEMETERPerturbations ionosphériques associées aux émetteurs VLF
DEMETEREffets des émetteurs VLF sur les ceintures de radiation
DEMETEREclipse 29 Mars 2006
Effets dans l’ionosphère supérieure
DEMETEREclipse 29 Mars 2006
Effets dans l’ionosphère supérieure
Observations DEMETER Modélisation SAMI2
DEMETERMSTID et ondes de gravité
Data comparison at the same conjugate points of different altitudes (300km and 660km)
DEMETERPropagation des perturbations dans l’ionosphère supérieure
F-peak 300kmF-peak 300km
DEMETER 660kmDEMETER 660km
Ionosphèrecollisionnelle
Ionosphèrenon collisionnelle
≤ 400 km
Normal SAMI2 SimulationNormal SAMI2 Simulation SAMI2 Simulation with MSTIDSAMI2 Simulation with MSTID
Difference
DEMETERModélisation ionosphérique SAMI2
The difference of 2 results illustrates a propagation of MSTID perturbation along B-field. Propagation reaches to the other hemisphere.
The difference of 2 results illustrates a propagation of MSTID perturbation along B-field. Propagation reaches to the other hemisphere.
Phase differences of observed parameters and their orders correspond well between the observation and a simulation.
Phase differences of observed parameters and their orders correspond well between the observation and a simulation.
DEMETERComparaison Observations Simulations
Ion Acoustic wave in SAMI2 for each ion species
SAMI2: Plasma Propagation
Propagation speed matches to that of the ion acoustic wave of the major ion species (H+) at high altitudesPropagation speed matches to that of the ion acoustic wave of the major ion species (H+) at high altitudes
The Magnetic Storm of November 7 to 10, 2004
Orbits with plasma depletions
Nigh-time Orbit 1903
Equatorial Plasma depletion
and Plasma waves
Electrostatic Turbulence at boundaries
Continuous ELF EM emissions
Burst of LH turbulenceTriggered by whistlers
DEMETER orbit
F-layerplasma velocity in depletion
LH Emissions
Solitary Structures
1- Bursts of electrostatic LH turbulence triggered by strong whistlers, High intensity, 104 µV2/m2.Hz at ωLH
Relaxation time ~ 10s
2- Evolve as solitary, monochromatic LH structures Large amplitude (~10 mV/m) wave packets, duration ~ 20 ms, Most often detected in localized density holes (ΔNi/Ni ~ -10% to -15%)
Interpretation
LH turbulence: scattering of whistler waves by pre-existing irregularities (e.g. Bell and Ngo, 1990)
LHSS as eigenmodes of cylindrical magnetic field aligned depletions (e.g. Schuck et al., 1998)
Lower Hybrid Emissions
LH emissions and ion heating
Super-thermal ion tails
Ion Heating
1- Super-thermal ions detected in deep plasma depletions
- simultaneous with LH turbulence and solitary structures
- heavy ions O+, NO+
2- No heating of the core ion distribution
stays at constant moderate temperature ~ 1200°K
3- Development of a super-thermal ion tail
typical: Nhot/Ncold~1-5%, Thot ~ 1 to 3 eV (~ 10 to 30 Tcold)
Interpretation- Heating by LH solitary waves
- Mechanism? resonant interaction unlikely since VLH >>Vthi
EQUATORIAL PLASMA BUBBLES
AND IONOSPHERIC OBSERVATIONS
BY DEMETER.
Summary of main observations
1- Deep plasma depletions (similar to SIBB, Kil et al., 2003) - consequence of the previous rise of the bottomside F-layer - downward plasma motion and bifurcation
2- ELF EM waves - Magnetospheric Line Radiations - trapped/ducted in deep and large depletions
3- LH turbulence and LHSS - LH turbulence due to scattering of high amplitude whistlers by irregularities - LHSS as eigenmode of magnetic-field aligned small scale irregularities
4- Ion Tail Heating - Interaction with LHSS, but mechanism TBD.