Effects of Heavy Ions on Ring Current Dynamics and EMIC Waves Excitation

1. Effects of Heavy Ions on Ring Current Dynamics and EMIC Waves Excitation • Vania K. Jordanova • Space Science and Applications, Los Alamos National Laboratory, • Los Alamos, NM 87545, USA • Self-consistent simulations of ring current H+, O+, and He+ ion dynamics and EMIC waves excitation during geomagnetic storms • Comparison of model results with in situ energetic particle data • Effects of EMIC waves scattering on: • ring current evolution, • subauroral proton arcs, • radiation belt dynamics • Acknowledgments: • Y. Miyoshi, Solar-Terrestrial Environment Laboratory, Nagoya, Japan • M. Thomsen and G. Reeves, Los Alamos National Laboratory, NM • M. Spasojevic, Stanford University, Packard Building, Stanford, CA • R. Thorne and Y. Dotan, Dept of Atmospheric Sciences, UCLA, CA SM35A-03, WPGM 2006

2. First Magnetic Storm Models Interactions between ring current and plasmaspheric populations • Injection & Radial diffusion • Plasma wave excitation • Outward expansion of the plasmasphere [Cornwall et al., 1970, 1971]

3. Global Imaging of the Inner Magnetosphere •Simultaneous images of the plasmasphere and the ring current by the IMAGE mission during the storm main phase (Dst = -133 nT) on May 24, 2000 EUV image of the plasmasphere at 0633 UT from above the north pole Superimposed HENA image of 39-60 keV fluxes showing significant ion precipitation near dusk •The low altitude ENA fluxes peak near dusk and overlap the plasmapause [Burch et al., 2001]

4. Wave Generation in Realistic Magnetospheric Plasma [Kozyra et al., JGR, 1984]

5. Normalized Energy of Resonant Protons Figure 1.Normalized parallel energies in units of B2/8Ne of protons resonating with EMIC waves in plasma consisting of (left) 77% H+, 20% He+, and 3% O+; (middle) of 90% H+, 9.8% He+, and 0.2% O+; and (right) in pure electron-proton plasma. The frequency is normalized to the proton gyrofrequency. Twenty negative (solid lines) and positive (dashed lines) harmonics are considered. [Jordanova et al., JGR, 1996]

6. Charge Exchange & Wave-Particle Interactions (WPI) Lifetimes Lifetime of ring currentprotonsdetermined by: charge exchangelosses WPI inelectron-protonplasma WPI in plasma consisting of77% H+, 20% He+, and 3% O+ L=4 & Ne=500 cm-3 [Jordanova et al., JGR, 1996]

7. Kinetic Model of the Ring Current - Atmosphere Interactions RAM --- Jordanova et al. [2001; 2006] Calculates the distribution function of ring current H+, O+, and He+ ions and thermal plasma from the fundamental kinetic equations plasma sheet - LANL sources initial distribution - Polar charge exchange Ring current model Coulomb collisions losses E=100 eV – 400 keV PA= 0º – 90º dipole (L= 2.0-6.5) all MLT atmospheric loss w-p interactions escape from MP transport convection & radial diffusion Plasmasphere model ionosphere/thermosphere

8. EMIC Waves Observations Freja data, April 2-8, 1993 storm, Dst=-170 nT, Kp=8- •Waveamplitudesdecreased with storm evolution •Wavesbelow O+ gyrofrequencyobserved near Dst minimum [Braysy et al., 1998] EMIC waves recorded using DE1 magnetometer within 30° MLAT during the 10-year mission lifetime [Erlandson and Ukhorskiy, 2001]

9. Self-Consistent Wave-Particle Interactions Model • Solve the hot plasma dispersion relation for EMIC waves: where nt, EII, At are calculated with our kinetic model for H+, He+, and O+ ions • Integrate the local growth rate along wave paths and obtain the wave gain G(dB) • Use a semi-empirical model to obtain the wave amplitude Bw from the wave gain G: • Or, use the analytical solution of the wave equation to relate the wave amplitude to G: Bw=Boexp(G), where Bo is a background noise level [Jordanova et al., JGR, 1997; 2001]

10. HOTRAY Model Results Main phase of a large geomagnetic storm: 04 UT, Nov 4, 1993 MLT=17 (a) Thermal electron density in the equatorial plane from RAM (circles) and the fit used in HOTRAY (solid). Also shown is the hot H+ (squares) and O+ (triangles) density. (b) Wave gain from RAM without plasmapuase enhancement (circles) and HOTRAY (solid). [Kozyra et al., Geophys. Monogr. Ser., 1997] (a) The ray path and (b) the path-integrated gain for guided EMIC waves launched from below the magnetic equator near L=4.25 [Thorne and Horne, JGR, 1997]

11. Diffusion Coefficients and Timescales Main phase of a large magnetic storm: July 13-18, 2000 Bw=0.5 nT =12.5 hrs Hour 12 L=5.5 MLT=16 Energies: 68 keV 20 keV 8 keV 3 keV Bw=9.4 nT =10 min

12. Effects of Wave-Particle Interactions RAM results & HYDRA data comparison: • Pitch anglescattering has larger effect thanenergydiffusion • Non-localeffects of WPI due to transport [Jordanova et al., GRL, 1998]

13. • Data are from the southern pass at MLT~18 and E=20 keV at hour~8.5 (middle) and at hour~25.5 (right) • Isotropic pitch angle distributions, indicating strong diffusion scattering are observed at large L shells near Dst minimum • Partially filled loss cones, indicating moderate diffusion are observed during the recovery phase •Empty loss cones, indicating no diffusion are observed at MLT~6 Ion Pitch Angle Distributions: POLAR/IPS

14. RAM Results: Precipitating Proton Flux Simulations at 09 UT, January 10, 1997: (a) and (b) using Volland-Stern model (c) and (d) using AMIE model • Stronger ring current builds up and larger amplitude waves are excited when AMIE model is used • Precipitating H+ fluxes are significantly enhanced by wave-particle interactions • Their temporal and spatial evolution is in good agreementwith POLAR/IPSdata at low L

15. Subauroral Proton Arcs: Observations and Modeling RAM simulations: June 17-18, 2001 Hours after 00 UT, June 17, 2001 Direct link between a subauroral arc and a global observations of a plasmaspheric plume by IMAGE [Spasojevic et al., 2004] EMIC waves are excited near hours 37- 40 in the afternoon MLT sector causingintense ion precipitation[Jordanova et al., 2006]

16. EMIC Waves Excitation and Ion Precipitation: October 2001 GEM Storm • We calculated the wave growth of EMIC waves from theHe+ band(between O+ and He+ gyrofrequency) • Intense EMIC waves are generated nearDst minima and during the recovery phase • Ion precipitationis significantly enhanced within regions of EMIC wave instability co-located with enhanced cold plasma density

17. Proton Ring Current Energy Losses: October 2001 • Proton precipitation losses become of the order of charge exchange losses near minimum Dst when radial diffusion and WPI are considered

18. Radiation Belt Modeling Challenges: Self-consistent WPI EMIC wave distribution (from RAM-ion) whistler mode wave distribution (from RAM-e) Developing acoupled ring current-radiation belt modelincluding self-consistent wave-particle interaction with EMIC and whistlermode plasma waves

19. RAM Results: Radiation Belt Electron Pitch Angle Distribution

20. Summary and Conclusions • The generation and propagation of EMIC waves depend strongly on the presence of both cold and energetic heavy ions (mainly He+ and O+) in the plasmas • Ring current ions resonate at lower energies in a multi-component plasma and the ion diffusion lifetimes decrease at ~tens of keV energies, causing stronger precipitation losses than in an electron-proton plasma • The growth of EMIC waves is enhanced after the fresh ion injection from the magnetotail and westward ion drift through the duskside magnetosphere. It reaches maximum in the postnoon MLT sector within regions of enhanced cold plasma density and plasmaspheric plumes • Wave-particle interactionsenhance significantly the ion precipitation. The temporal and spatial evolution of precipitating H+ fluxes was in good agreementwith IMAGE FUVobservations • Ring current precipitation losses become of the order of charge exchange losses when strong waves are excited near Dst minimum • An initial simulation with RAM of radiation belt electron dynamics showed that EMIC waves cause pitch angle scattering for MeV electrons