1. Influence of EMIC Waves on Radiation Belt Dynamics T. Kersten, R. B. Horne, N. P. Meredith, S. A. Glauert ESWW11 Liège, 17-21/11/2014 British Antarctic Survey, UK

2. Van Allen Radiation Belts Inner belt: stable Outer belt: highly variable Main cause for variability: Plasma waves Risk for spacecraft Source: NASA

3. Types of Plasma Waves Chorus waves: –Major cause of acceleration and loss Chorus Sun Magnetopause Plasmaspause

4. Types of Plasma Waves Chorus waves: –Major cause of acceleration and loss Magnetosonic waves: –May be an important acceleration mechanism Chorus Sun Magnetosonic waves Magnetopause Plasmaspause

5. Types of Plasma Waves Chorus waves: –Major cause of acceleration and loss Magnetosonic waves: –May be an important acceleration mechanism Plasmaspheric hiss: –Major loss process Chorus Sun Magnetosonic waves Plasmaspheric hiss Magnetopause Plasmaspause

6. Types of Plasma Waves Chorus waves: –Major cause of acceleration and loss Magnetosonic waves: –May be an important acceleration mechanism Plasmaspheric hiss: –Major loss process ElectroMagnetic Ion Cyclotron (EMIC) waves: –H + : f cHe < f < f cH –He + : f cO < f < f cHe Chorus EMIC waves Sun Magnetosonic waves Plasmaspheric hiss Magnetopause Plasmaspause

7. Types of Plasma Waves Chorus waves: –Major cause of acceleration and loss Magnetosonic waves: –May be an important acceleration mechanism Plasmaspheric hiss: –Major loss process ElectroMagnetic Ion Cyclotron (EMIC) waves: –H + : f cHe < f < f cH –He + : f cO < f < f cHe –May be important loss process Objective of Study: Quantify losses caused by EMIC waves Chorus EMIC waves Sun Magnetosonic waves Plasmaspheric hiss Magnetopause Plasmaspause

8. Fokker-Planck Equation BAS Radiation Belt Model

9. Fokker-Planck Equation BAS Radiation Belt Model Radial transport

10. Fokker-Planck Equation BAS Radiation Belt Model Radial transportPitch angle diffusion

11. Fokker-Planck Equation BAS Radiation Belt Model Energy diffusionRadial transportPitch angle diffusion

12. Fokker-Planck Equation BAS Radiation Belt Model Energy diffusionLossesRadial transportPitch angle diffusion

13. Fokker-Planck Equation Drift & bounce averaged diffusion coefficients D LL, D αα, D EE are activity, location and energy dependent Details in: Glauert et al. 2014 BAS Radiation Belt Model Energy diffusionLossesRadial transportPitch angle diffusion

14. Calculating the Diffusion Coefficients Use the PADIE code (Glauert and Horne, 2005) Requires Gaussian distribution

15. Calculating the Diffusion Coefficients Use the PADIE code (Glauert and Horne, 2005) Requires Gaussian distribution –Peak power: I W

16. Calculating the Diffusion Coefficients Use the PADIE code (Glauert and Horne, 2005) Requires Gaussian distribution –Peak power: I W –Peak of the Gaussian fmfm

17. Calculating the Diffusion Coefficients Use the PADIE code (Glauert and Horne, 2005) Requires Gaussian distribution –Peak power: I W –Peak of the Gaussian –Width of the Gaussian fmfm df

18. Calculating the Diffusion Coefficients Use the PADIE code (Glauert and Horne, 2005) Requires Gaussian distribution –Peak power: I W –Peak of the Gaussian –Width of the Gaussian –Cut-off frequencies fmfm df

19. Calculating the Diffusion Coefficients Use the PADIE code (Glauert and Horne, 2005) Requires Gaussian distribution –Peak power: I W –Peak of the Gaussian –Width of the Gaussian –Cut-off frequencies Model for plasma density fmfm df

20. Calculating the Diffusion Coefficients Use the PADIE code (Glauert and Horne, 2005) Requires Gaussian distribution –Peak power: I W –Peak of the Gaussian –Width of the Gaussian –Cut-off frequencies Model for plasma density Ion composition fmfm df

21. CRRES EMIC Wave Database Contains: Peak frequency f m Spectral width d f Peak intensity I 0 EMIC wave events binned by: L*, MLT, 5 magnetic activity levels Average intensities – Helium band Average intensities – Hydrogen band

22. Modelling the Radiation Belts

23. EMIC Diffusion Rates Pitch angle diffusion coefficient (s -1 )

24. EMIC Diffusion Rates 1 MeV

25. Combined EMIC and Chorus Diffusion Rates

26. Electron flux: 100 day simulation – 90° 90° flux (cm -2 sr -1 s -1 keV -1 ) for 6MeV electrons With EMIC Without EMIC

27. Electron flux: 100 day simulation – 90° 90° flux (cm -2 sr -1 s -1 keV -1 ) for 6MeV electrons With EMIC Without EMIC

28. Electron flux: 100 day simulation – 45° 45° flux (cm -2 sr -1 s -1 keV -1 ) for 6MeV electrons With EMIC Without EMIC

29. Electron flux: 100 day simulation – 45° 45° flux (cm -2 sr -1 s -1 keV -1 ) for 6MeV electrons With EMIC Without EMIC

30. Pitch-angle distribution: 1 MeV

31. Pitch-angle distribution: 6 MeV

32. Pitch-angle distribution: 10 MeV

33. Conclusions EMIC waves lead to significant losses at pitch-angles < 60° EMIC waves are effective at scattering electrons for E > 2MeV There is no significant energy diffusion EMIC waves will result in a peaked particle distribution for 70° < α < 90° Therefore, we suggest: Looking for particle distributions peaked near 90° and E > 2MeV in Van Allen Probes data

34. Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreements number 262468 (SPACECAST) and number 284520 (MAARBLE), and is also supported in part by the UK Natural Environment Research Council

35. Wave parameters ParameterHydrogen band wavesHelium band waves f m /f cH 0.40.15 df/f cH 0.02 f lc /f cH 0.360.11 f uc /f cH 0.440.19 XmXm 0.0 ΔXΔXtan 15° X cut 2 ΔX Resonances-10 ≤ n ≤ 10 f pe /f ce 10.0 Ion composition94% H + 5% He + 1% O +