Rponse globale de la thermosphre aux vnements solaires

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Réponse globale de la thermosphère aux évènements
solaires

• Létat de la thermosphère dépend des apports
  dénergie
• EUV solaire
• - Joule et particulaire déposée en zone aurorale

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The method
Running SVD analysis over 15 consecutive orbits
(about 1 day)
TOTAL MASS DENSITY at the satellite altitude
(10-15 g/cm3)
10 LT
22 LT
The projection on the first component accounts
for large scale variations spatial variations
are captured by the first principal component,
and time variations are captured by the
associated projection coefficient C1.
Residuals account for smaller scales, as tides
and gravity waves
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Définition dun proxy thermosphérique
CHAMP data
NRLMSISE-00 model with MgII proxy and ap
NRLMSIS_quiet with MgII proxy and Ap4
Normalized coefficient C1 CHAMP / C1
NRLMSIS_quiet C1 NRLMSIS/ C1 NRLMSIS_quiet
MgII proxy The composite MgII index (Viereck et
al, 2004) is used as a proxy for solar EUV
instead of F10.7
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NRLMSIS_quiet is used as a reference, that
accounts for LT, seasonal variations, solar
activity
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• Statistical analysis binning of normalized C1
  coefficients as a function of ap

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Comparaison avec le modèle
Day time
Night time
Density perturbation
ap index
ap index
correlation coefficient between CHAMP data and ap
x CHAMP data x NRLMSIS model
Binning is done using the value of ap from the
previous 3 hour interval
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Comparaison Jour - Nuit
CHAMP Data
Model
Density perturbation
am index
am index
x Day time x Night time
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x Day time Night time
Linear fit y 1.9 x 0.9
Binning with ap
Binning with am
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Density perturbation CHAMP data and NRLMSIS
model
Day of 2004
- the model seems to correctly represent the
shape of the perturbation but greatly
underestimates its magnitude.
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11
17 et 21 Janvier 2005
Mai 2003
Halloween storm
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Jour 12 LT
Nuit 0 LT
13
Soir 20 LT
Matin 8 LT