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Wave Particle Diffusion of Energetic Ring Current Ions

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Wave Particle Diffusion of. Energetic Ring Current Ions. S. Jones USRA ... Electromagnetic Ion-Cyclotron (EMIC) waves are generated by pitch-angle anisotropy ... – PowerPoint PPT presentation

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Title: 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
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