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Theory and simulation predict:

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Theory and simulation predict:

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  1. Cusp Radiation Source: A Challenge for Theory and SimulationJiasheng Chen, Theodore A. Fritz, Katherine E. Whitaker,Forrest S. Mozer, and Robert B. SheldonIn cooperation with:J. F. Fennell, M. Klida, K. Kudela, V. N. Lutsenko,J. Niehof,J. S. Pickett, J. Roeder, C. T. Russell, G. L. Siscoe, W. N. Spjeldvik, and K. Trattner

  2. Theory and simulation predict: • Cusp is a precipitation region for particles; • A positive IMF By would move the dayside northern cusp into post-noon; • A negative IMF Bywould move the dayside northern cusp into pre-noon (e.g., Cowley et al., JGR, 96, 5557, 1991).

  3. Cusp Diamagnetic Cavities (CDC): |B| with turbulence. Cusp energetic Particle (CEP) CDC at 9:30 MLT (pre-noon)

  4. CDC at 14-23 UT on 5/13/99 with a size of ~ 6 Re. Cusp

  5. Solar wind conditions for the 5/13/99 CDC Since By < 0, a CDC at pre-noon was expected. By < 0

  6. Other CDC observations under different solar wind conditions: • Normal solar wind speed, vsw = 450 km/s • Fast solar wind stream, vsw = 900 km/s • Slow solar wind flow, vsw = 380 km/s (two examples presented)

  7. 1. Normal solar wind speed, vsw=450 km/s 4/22/99

  8. Pre-noon Post-noon (Fritz et al., JGR, 108, A1, 1028, 2003)

  9. By>0, <Dst>=1.6 nT, CDC at pre-noon; unexpected By>0 CDC at 10:30 MLT

  10. 2. Fast solar wind stream, vsw=900 km/s 6/28/99

  11. Cusp energetic He++ Cusp energetic O+

  12. By>0, <Dst>=14.7 nT, CDC at 7MLT;unexpected + + CDC

  13. 3a. Slow solar wind flow, vsw=380 km/s 4/25/99

  14. POLAR, 4/25/99

  15. By>0, <Dst>=5.5 nT, CDC at pre-noon;unexpected By>0 CDC at 10:20 MLT

  16. 3b. Slow solar wind flow, vsw=380 km/s 19 UT 15 UT 15 UT 19 UT

  17. By>0, <Dst>=-82 nT, CDC at 8:30 MLT;unexpected ISEE-3 10/30/78 IMF By>0 CDC ISEE-1

  18. Energetic Charged Particles in CDC CEP electron CEP proton CDC

  19. CEP Energy Spectrum

  20. CEP vs. Outer Radiation Belt ParticlesProton phase space density

  21. He++ & O+ phase space densities: Cusp Radiation Source

  22. CEP and Fields • CEP flux increase • with E-field increase • and B-field Decrease. • 2. Emax = 50 mV/m

  23. Blow up cusp E-field near peak fluctuation Showing some polarization Waves at different Frequencies.

  24. Left-hand polarization

  25. Left-hand polarization

  26. Summary • CDC is a large radiation region, and CEP is a new radiation source. • Under different solar wind and geomagnetic conditions, CDCs have been observed at pre-noon in the northern hemisphere when IMF By >0 (duskward). • These observations are unexpected by the existing models and MHD simulations and provide a new challenge for the current theory and simulations. • Cusp ions can be energized by both resonant and stochastic acceleration mechanisms.

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