Presentation on theme: "Forecasting the high-energy electron flux throughout the radiation belts Sarah Glauert British Antarctic Survey, Cambridge, UK SPACECAST stakeholders meeting,"— Presentation transcript:
Forecasting the high-energy electron flux throughout the radiation belts Sarah Glauert British Antarctic Survey, Cambridge, UK SPACECAST stakeholders meeting, BAS, 7 February 2014
Electron Radiation Belts High energy electrons (E>500 keV) are trapped by Earth’s magnetic field Form two torus shaped regions around earth –Inner belt 1.2 < L < 2 Fairly stable –Outer belt 3 < L < 7 Highly dynamic Slot region lies between the two belts –During active conditions the flux in this region can be significant (>10 3 cm -2 s -1 sr -1 keV -1 for 1 MeV electrons)
Motion of trapped electrons An electron’s motion is constrained by the magnetic field 3 parts: Orbiting round the field line Bouncing along the field line Drifting between field lines Modelling uses a coordinate system related to magnetic field: L (L*) is the distance from the centre of the Earth to the equatorial crossing of the field line measured in Earth radii
A few minutes in the life of an MeV electron Chorus Hiss EMIC Electron drift path Magnetopause Magnetic field fluctuations driven by ULF waves Loss and acceleration Loss Everything is location, geomagnetic activity and energy dependent
chorus waves plasmapause Chorus - outside the plasmapause Chorus and Hiss Time hiss Hiss – inside the plasmapause
Radiation Belt Models SPACECAST has 2 radiation belt models: BAS Radiation Belt Model Salammbô – ONERA Developed independently Calculate the high-energy electron flux throughout radiation belt Include the effects of Radial transport Interactions between electrons and electromagnetic waves Collisions between electrons and the atmosphere Models have been adapted for use in forecasting Models have been improved during the project
Radiation Belt Models Equation used in modelling (don’t panic!): Includes the physical processes present in the radiation belts Many parameters describe the different processes –Using correct values for these parameters is crucial
Describing the waves A good description of the interaction between the waves and the electrons is vital for accurate modelling Build global maps of the wave properties Use these to determine parameters in the models Intensity of the waves Increasing geomagnetic activity Earth
CRRES data Just radial transport Radial transport and hiss Radial transport, hiss and chorus Role of the different processes
510 keV electrons Simulation with radial diffusion, hiss and chorus GPS Galileo Slot region CRRES data Data Model
High-energy electron forecasts - 1 Detailed forecast of flux –Simulation of last 24 hours –Forecast of next 3 hours Various energies available –300, 800, 2000 keV –>100, >300, >800, >2000 keV Solar wind parameters and magnetic indices also shown
High-energy electron forecasts - 2 24 hour fluence >2MeV electrons Related to internal charging Produced for GEO, MEO and slot region
Validation GOES flux for >800 keV and >2MeV electrons –Comparison with GOES data shown for each forecast –Geostationary orbit only CRRES data –Data from across whole outer radiation belt –See what the models would have predicted and compare –Less than 2 years data from 1990-1991 Galileo data (SREM instrument on Giove-B) –Counts not flux so comparison is difficult Van Allen Probes –Great data set for future work We need more data
Summary of developments in SPACECAST Research models have been developed into forecasting models –Forecast 3 hours ahead every hour Forecasts available on the web www.fp7-spacecast.eu –Variety of formats Models have improved but there is still more work to do
Questions 1.What information would be useful that we don’t currently provide? 2.We show flux at geo because we have GOES data for comparison a)We can calculate flux along other orbits – which? b)Would the flux, fluence or risk at particular satellites be useful? 3.Risk indices a)Are these useful? b)Are we using the right measurement and thresholds? c)Would you be interested in customising these? 4.We can simulate periods in the past and calculate the flux/fluence encountered by a satellite a)Would anyone use this for post-event analysis?
High-energy electron risk index Based on the 24 hour electron fluence (F) for >2MeV electrons Electron fluence: electron flux integrated over 24 hours (cm -2 sr -1 ) The risk index is set according to : High F > 5x10 8 electrons cm -2 sr -1 Medium5x10 7 ≤ F ≤ 5x10 8 electrons cm -2 sr -1 LowF < 5x10 7 electrons cm -2 sr -1 Threshold values above which internal charging occurred on particular satellites at geosynchronous orbit [Wrenn et al., 2002]. Wrenn, G. L., D. J. Rodgers, and K. A. Ryden (2002), A solar cycle of spacecraft anomalies due to internal charging, Ann Geophys., 20, 953–956.
High-energy electron forecasts - 2 24 hour fluence >2MeV electrons Related to internal charging Produced for GEO, MEO and slot region Still too much information? High risk Low risk
High-energy electron forecasts - 3 Based on the 24 hour electron fluence (F) for >2MeV electrons: HighF > 5x10 8 electrons cm -2 sr -1 Medium 5x10 7 ≤ F ≤ 5x10 8 electrons cm -2 sr -1 LowF < 5x10 7 electrons cm -2 sr -1 [Wrenn et al., 2002].
High-energy electron radiation belt forecast models (Work package 401) Background Physical processes in the radiation belts Radiation Belt models Forecasting the high-energy electron radiation belts Validation Progress made in SPACECAST