High Speed Streams & Earth’s Quadrupole Cusp: Implications for ORBE

1. High Speed Streams & Earth’s Quadrupole Cusp: Implications for ORBE R. B. Sheldon, NASA/MSFC/NSSTC T. Fritz & J.-S. Chen, CSP/BU Manaus, Brazil Feb 10, 2005

2. The Oldest Physics Problem • How does point A influence point B? • Aristotle: mind, “spooky action at a distance” • Democritus to Descartes: particles • Newton: gravity (e.g. tides) • Huygens: waves • Faraday: fields • How does the Sun transfer energy to Earth? • Photons & protons (DC equilibrium): pressure, heat • Waves & impulsive events (AC mechanical): Alfvenic, compressional, shocks • Electric & Magnetic fields (AC/DC): currents

3. Sun-Earth Transducers • Proton pressure  Bow shock, hot plasma (100eV electron, 1 kev/nuc ion), thermalized ram energy “Frictional” or “viscous” (rV5/2) • Impulsive  SSC, shock acceleration, Fermi, radial diffusion, Kp, “mechanical” (rV2) • Fields  Polar cap potential, convection, ring current, Dst, AE, “electrical” (V*Bz) [ICME] • What transducer is CIR ORBE? Poor correlation of ORBE with all of the above! Best with Vsw.

4. Springs & Shock Absorbers • Why does a car have BOTH springs & shocks? • Springs are “reversible”, adiabatic, they “bounce back” (and ruin the tire tread). • Shock absorbers are “irreversible”, non-adiabatic, they convert the energy to heat. • Ex: manual dynamo with lightbulb or with 1F capacitor. • Vsw energy transducer must be irreversible. • Cannot be too “stiff”, ideally it is “critically damped” • Magnetic fields are “springy”, what are “shocks”? • Something responding to Vsw, yet not stiff…

5. The Quadrupole Cusp -- Static Equilibrium

6. The Dipole Trap • Great Trap • Poor accelerator • ENA of E >1 keV particles outside trap.

7. Quadrupole Trap in the Laboratory(Two 1-T magnets, -400V, 50mTorr)

8. Maxwell 1880 Chapman 1930

9. QuadrupolarT87 Magnetosphere • All modern B-models have high latitude cusps. • Since Chapman & Ferraro 1937, we’ve known the magnetosphere is a quadrupole, yet all the trapping models to the present have assumed a dipole.

10. B-field lines Cusp Equator |B| C=1 C=1.5 C=2

11. The Simulated T96 Quadrupole Trap • Lousy Trap • Great Accelerator • Can be made to trap better though.

12. Chaotic, nearly trapped

13. H+ Trapping in T96 Cusp

14. e- Trapping of T96 Cusp

15. Cusp Provisional Invariants • Minimum energy, Emin, is defined by “separatrix” energy (ExB = B) ~ 30 keV • Max energy, Emax, defined by rigidity.~ 3 MeV e- • Mapping cusp Energy limits to the rad belts, give ~ 0-100 keV for protons, and 1-5 MeV for electrons. • Mapping C-shell limits to the dipole give ~4<L<∞. very close to the PSD “bump” • Mapping pitchangles  50o < a < 90o at dipole eq. • Cusp particles have all the right properties ORBE

16. The Outer Radiation Belt Electrons (ORBE)

17. McIlwain, 1966

18. ORBE (McIlwain 1966)

19. McIlwain 1966

20. Empirical Prediction • McIlwain 1966: Geo MeV e increases • Paulikas & Blake 1979: Vsw best external • Nagai 1988: Kp best internal predictor • Baker 90 LPF, Koons&Gorney 90 NN • Dmitriev&Chao03 Log-Linear • Ukhorskiy et al., 04 NonLinear

21. Correlations • Highest SW correlation for energetic particles in the radiation belts is: velocity. R=.7-.8 during high-speed streams) • V is NOT an energy. Not a density. Nor a Force(mv) • Multiplying by density  ram or mechanical energy, makes the correlation worse. • Multiplying by Bz  Electrical energy, makes the correlation worse. • Whatever the mechanism, it is not energy-starved (2nd moment) or density starved (0th moment).

22. 1996

23. The Discovery of Cusp MeV Electrons

24. POLAR: Oct 12-16, 1996

25. Sheldon et al., GRL 1998 POLAR/ CAMMICE data 1 MeV electron PSD in outer cusp

26. POLAR 4/1/97 Cusp Traversal

27. Accelerator Efficiency Why would the cusp accelerate at all? Why not just use standard well-known accelerators?

28. The Dipole Trap “Accelerator” • The dipole trap has a positive B-gradient that causes particles to trap, by B-drift in the equatorial plane. Three symmetries to the Dipole each with its own “constant of the motion” 1)Gyromotion around B-field Magnetic moment, “”; 2) Reflection symmetry about equator Bounce invariant “J”; 3) Cylindrical symmetry about z-axis Drift invariant “L” Betatron acceleration by E┴ compression, violation of 3rd invariant, L-shell

29. The 1-D Fermi-Trap Accelerator Waves convecting with the solar wind, compress trapped ions between the local |B| enhancement and the planetary bow shock, resulting in 1-D compression, or E// enhancement. Pitchangle diffusion keeps it in.

30. The 2-D Quadrupole Trap • A quadrupole is simply the sum of two dipoles. • Quadrupoles have “null-points” which stably trap charged particles (eg. Paul trap) • Motion of the dipoles results in a 2D constriction of the volume. This is just a generalization of 1D Fermi-acceleration to 2D. • 1D Fermi acceleration increases E//, violating the 2nd invariant. • 2D betatron acceleration increases E┴ , violating the 1st & 3rd invariants

32. Model • Fast solar wind is trapped in the cusp • 27 day recurrence, non-linear with Vsw • High Alfvenic turbulence of fast SW heats the trap • Low Q-value, compressional, BEN • 2nd Order “Fermi” accelerates electrons • Low energy appear first, then high w/rigidity cutoff. • Trap empties into rad belts simultaneous L=4-10 • “gentle” evaporation, or “rapid” topology change • Initially “butterfly” around 70-deg equatorial

33. 1. Non-Linear Vsw Dependence 30keV 100eV 10keV 1keV Vsw Flux Flux seed trap seed trap E E The Reason that Vsw interacts non-linearly is that it does several things at once. It heats the seed population, while also making the trap deeper.

34. Kolmogorov, Arnol’d, Moser (applied to Jupiter perturbation of Earth)……… Earth orbit as Perturbed by Jupiter. Poincaré slice x vs. vX taken along the E-J line. Earth orbit if Jupiter were 50k Earth masses.

35. T96 Cusp Topology Solstice 4UT Solstice 16UT Equinox 16UT Equinox 16UT,-Bz

36. Cusp Feedback But the cusp is turbulent! How ca n the REAL cusp trap anything for 2 days!? It doesn’t. Usually.

37. Cusp Diamagnetic Cavitiesa.k.a Magnetic Bubbles

38. Diamagnetic Effect of Cold Plasma

39. An Interplanetary Test

40. Cusp Scaling Laws • Maximum energy from rigidity cutoffs, scaled by distance of planetary cusp to surface of planet. • Assuming: • Brad ~ Bsurface= B0 • Bcusp ~ B0/Rstag3 • Erad= 5 MeV for Earth • Ecusp ~ v2perp~ (Bcuspr)2 ~ [(B0/Rstag3)Rstag] • m = E/B is constant Erad-planet~(Rstag-Earth/Rstag-planet)(B0-planet/B0-Earth)2Erad-Earth

41. Scaled Planetary ORBE Planet Mercury Earth Mars Jupiter Saturn Uranus Neptune R STAG 1.4 10.4 1.25 65 20 20 25 B0 (nT) 330 31,000 < 6 430,000 21,000 23,000 14,000 ERAD 4 keV 5 MeV < 1.5 eV 150 MeV 1.2 MeV 1.4 MeV 0.42 MeV

42. Conclusions • The quadrupole is a nearly universal trap and cosmic accelerator more efficient than Fermi (and shocks). • The quadrupole cusp has ideal properties to couple AC mechanical energy from SW into the magnetosphere. • The peculiar correlations of ORBE with SW can be explained by requiring an intermediate stage of the non-linear cusp. • A test of the mechanism using comparative magnetospheres shows the correct energy scaling. Soli Deo Gloria