Wave Particle Diffusion of Energetic Ring Current Ions

1
Wave Particle Diffusion of Energetic Ring
Current Ions

• S. Jones USRA / NASA-GSFC
• M.-C. Fok NASA-GSFC
• K. Gamayunov NASA-MSFC

2
Outline

• EMIC Waves Pitch Angle Diffusion
• CRCM Model
• EMIC Calculation
• Nov 20-21 2003 Storm Simulation
• Conclusions

3
EMIC Waves Pitch Angle Diffusion

• During magnetic storm recovery, high energy ion
  populations have been observed to decay faster
  than can be explained by charge exchange losses
• Pitch-angle scattering by EMIC waves has been
  suggested as a mechanism to explain rapid ion
  loss
• Electromagnetic Ion-Cyclotron (EMIC) waves are
  generated by pitch-angle anisotropy
• Wave particle interactions may cause diffusion
  of high energy ions into the loss cone

4
CRCM Model

• Comprehensive Ring Current Model (CRCM) couples
  the Rice Convection Model (RCM) and the kinetic
  Fok ring current model
• RCM calculates ionospheric E field and current
• Fok model advances plasma distribution and
  particle losses
• Empirical Tsyganenko 89,96 and MHD
  BATS-R-US used as magnetic field models
• CRCM electric field drives plasmasphere model

5
EMIC Wave Growth Calculation

• EMIC growth driven by ring current ion
  temperature anisotropy
• CRCM simulates hot and cold plasma densities
• Convective growth rate (S) determined following
  Kozyra theory
• S scanned over normalized wave frequency for
  maxima
• S integrated along field lines for total wave
  gain G
• G used to estimate EMIC magnetic field (Bw)

6
Nov 20-21 2003 Superstorm
7
CRCM Results

• Initial run from the 20 Nov. 2003 superstorm
• Large Simulated hot ion temperature anisotropy
  (due to drift shell splitting) and EMIC waves in
  dayside at Lgt7
• Smaller wave growth in L4 extending from local
  noon to dawn during storm peak
• EMIC wave activity steady in L4 ring during
  storm recovery phase

8
Conclusions Future Work

• CRCM simulation equatorial flux persists during
  recovery
• High energy ions are observed to quickly decay
• In progress Khazanov/Gamayunov model to
  calculate pitch angle diffusion losses
• Compare diffusion losses with IMAGE and other
  observations