1 / 28

Cusp Radiation Sources: Unraveling Challenges for Theoretical Models and Simulations

This paper explores the cusp regions as significant precipitation zones for charged particles, focusing on the impact of interplanetary magnetic field (IMF) variations on cusp dynamics. By analyzing cusp diamagnetic cavities (CDCs) under different solar wind conditions, it presents unexpected observations that challenge existing theoretical models and magnetohydrodynamic simulations. The findings highlight the role of cusp energetic particles (CEPs) as new radiation sources, indicating that cusp ions can undergo energization through both resonant and stochastic mechanisms.

tiger-graves
Download Presentation

Cusp Radiation Sources: Unraveling Challenges for Theoretical Models and Simulations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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.

More Related