Trapped radiation models
D. HeynderickxBelgisch Instituut voor Ruimte-Aëronomie
Ringlaan 3, B-1180 Brussel
Galactic cosmic rays
Solar energetic particles
Secondary (albedo) radiation
Radiation belts
Earth’s Van Allen belts
• Particle motion: gyration, bounce, drift
• Guiding centre approximation: McIlwain’s (B,L) coordinates
• Model description: J(E,B,L)
Charged particle trapping
Trapped proton population
Trapped electron population
The South Atlantic Anomaly
• Low altitude part of radiation belts
• Tilt and shift of geomagnetic field: Fraser-Smith, Rev. Geophys., 25, 1, 1987
• Interaction with neutral atmosphere
http://www.spenvis.oma.be/spenvis/help/background/magfield/cd.html
The South Atlantic Anomaly (SAA)
Trapped proton variability
• Seasonal• Secular variation of
geomagnetic field• Impulsive
• Solar cycle
SAMPEX/PETAP-8 MIN
Directional proton flux >18 MeV at 500 km
Secular variation
Impulsive penetration
CRRESELE Equatorial L profiles
Parametrized in terms of Ap15: 15 day average of Ap
Available models
• De facto standard models: NASA AP-8 and AE-8– Advantages of the NASA models:
• Widespread usage (heritage)• Full spatial coverage and energy range
– Disadvantages of the NASA models:• Represent radiation environment of the 60’s and 70’s• Static models (but probably ok for long time averages)• Contamination by Starfish electrons
• Other models:– CRRESPRO, CRRESELE– NOAAPRO– POLE– SAMPEX/PET
Replacement of AP-8 and AE-8
• New models do not have sufficient spatial and/or temporal coverage and/or energy range
• Incomplete energy range can lead to misleading effects estimations
Standardisation efforts
• COSPAR Panel for Radiation Belt Environment Modeling (PRBEM) http://wwwe.onecert.fr/craterre/prbem/
• NASA working group meeting:– Focus efforts on selected regions of space and energy ranges to
expedite AP-8 and AE-8 replacement
– POLE model for GEO
– SAMPEX/PET+NOAAPRO for LEO protons
– ONERA/LANL GPS modelling for MEO
• RERMM study: use data from different satellites + Salammbô numerical simulation to produce ‘ad hoc’ models