mission demeter quelques résultats sur l’ionosphère

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.