Forecasting the high-energy electron flux throughout the radiation belts

1. Forecasting the high-energy electron fluxthroughout the radiation belts Sarah Glauert British Antarctic Survey, Cambridge, UK SPACECAST stakeholders meeting, BAS, 7 February 2014

2. 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 (>103 cm-2 s-1 sr-1 keV-1 for 1 MeV electrons)

3. 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

4. A few minutes in the life of an MeV electron Magnetopause Loss Loss Chorus Loss and acceleration Hiss Magnetic field fluctuations driven by ULF waves EMIC Loss Electron drift path Everything is location, geomagnetic activity and energy dependent

5. plasmapause chorus waves Chorus and Hiss hiss Frequency (kHz) Time • Chorus - outside the plasmapause • Hiss – inside the plasmapause

6. 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

7. 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

8. Describing the waves Increasing geomagnetic activity Earth 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

9. Role of the different processes CRRES data Just radial transport Radial transport and hiss Radial transport, hiss and chorus

10. CRRES data Data Model GPS Galileo Slot region 510 keV electrons Simulation with radial diffusion, hiss and chorus

11. 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

12. High-energy electron forecasts - 2 • 24 hour fluence >2MeV electrons • Related to internal charging • Produced for GEO, MEO and slot region

13. 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

14. 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 Summary of developments in SPACECAST

17. Questions What information would be useful that we don’t currently provide? We show flux at geo because we have GOES data for comparison We can calculate flux along other orbits – which? Would the flux, fluence or risk at particular satellites be useful? Risk indices Are these useful? Are we using the right measurement and thresholds? Would you be interested in customising these? We can simulate periods in the past and calculate the flux/fluence encountered by a satellite Would anyone use this for post-event analysis?

18. 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 : HighF > 5x108 electrons cm-2 sr-1 Medium 5x107 ≤ F ≤ 5x108 electrons cm-2 sr-1 Low F < 5x107 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.

19. High risk Low risk 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?

20. High-energy electron forecasts - 3 Based on the 24 hour electron fluence (F) for >2MeV electrons: High F > 5x108 electrons cm-2 sr-1 Medium 5x107 ≤ F ≤ 5x108 electrons cm-2 sr-1 Low F < 5x107 electrons cm-2 sr-1 [Wrenn et al., 2002].

21. 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