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Space Plasma Accelerators

Space Plasma Accelerators. Cosmic CERNs and SLACs Robert Sheldon Sept 22, 1998. Long-range Plasma Forces. The magnetosphere: a living thing Solarwind - M ’ sphere - Ionosphere The “ Constellation ” mission Polarwind - Plasmasphere

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Space Plasma Accelerators

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  1. Space Plasma Accelerators Cosmic CERNs and SLACs Robert Sheldon Sept 22, 1998

  2. Long-range Plasma Forces • The magnetosphere: a living thing • Solarwind - M’sphere - Ionosphere • The “Constellation” mission • Polarwind - Plasmasphere • G.Wilson: non-local Coulomb interaction: collisions in ionosphere heat plasmasphere • Solarwind - Heliopause • runaway electrons and shock heating (potato in the tailpipe) • FORGET IDEAL GASES!

  3. Plasma Spectra & Entropy • Maxwellian is the Maximum Entropy state: self-similar under interchange. • Power-law tails are NOT an entropy maximum. Space plasmas most often are described by “kappa-functions”, a Maxwellian + power law tail. “Matthew Principle”--the rich get richer. • Space plasmas are NOT at equilibrium • WHY? Long-range interactions. • Or, Space Plasma Accelerators

  4. Space Plasma Cyclotrons

  5. The Synchro-Cyclotron • The “resonance” condition for a cyclotron and the need for synchronization. • The maximum energy determined by maximum gyroradius of pole magnet • Center feed, rim exit. • Dipole=cyclotron • but NOT a betatron.

  6. x Drift Motion in B-field Gradients

  7. Universe has dipoles. Drift trapping more robust than gyrotrap because of edges. Stochastically driven has power at all freq. Adiabatic heating from inward diffusion (3rd invariant violation). Adiabatic central heating--> escaping flux is cooler. Rim feed, center exit. The center is filled with the magnet, limiting the energy. Diffusion rate slows near the center, limiting the power. The Stochastic Dipole Cyclotron PRO CON

  8. Insufficiency of the SDC • Although the radiation belts of the earth have 10’s MeV particles, GeV’s precipitate into the atmosphere, and “detrap” adiabatically, cooling to keV energies. From a Mars vantage point, the Earth dipole is a weak source of keV particles and atoms. Nor does adiabatic heating explain power law tails. The Dipole is a better trap than accelerator.

  9. MeV electrons 10/14/96

  10. T96 Cusp: Solstice & Equinox Solstice 16UT Solstice 4UT Equinox 16UT,-Bz Equinox 16UT

  11. 1 MeV electron in T96 Cusp

  12. The Quadrupole Cusp • 2-Dipole interactions = Quadrupole. A Dipole embedded in flowing plasma creates a quadrupole cusp. • How likely? About like binary stars. • Quadrupole is both a drift+gyro trap. • Q is center feed, rim exit. Hi E escape. • Q has no center magnet permitting higher maximum energies. • Q is NOT adiabatic==> chaotic accel!

  13. The Quadrupole Chaotic Cyclotron • The existence of 3 adiabatic invariants = stable trapped motion. In the dipole, Td:Tb:Tg::1000:1:.001 seconds. In the quadrupole they are 10:1:0.1 seconds. • In a perturbation field, they can random walk through phase space. • Stochastic Betatron acceleration is now possible, since the 1st invariant is not conserved. + Stochastic Cyclotron. • Result: Very efficient, fast acceleration

  14. Planetary Magnetospheres Stellar Heliospheres Binary stars Galactic magnetic fields Galaxy clusters keV (Mercury) to MeV (Jupiter) 10 - 100 MeV as observed at Sun 1-10 GeV 10-100 GeV ? TeV? Quadrupole Cosmic Scales

  15. Plasma Linear Accelerators

  16. Parallel Electric Fields • Whipple, JGR 1977. Ne = Ni, quasi-neutrality n F E kT || e

  17. Heuristics for Parallel-Efield

  18. Necessary Conditions • Inhomogeneous B-field such that grad-B drifts dominate over ExB • Dipole field! • Source of hot plasma • Injected directly (accretion disks) • Convected from elsewhere (plasmasheet)

  19. The Storm Linear Accelerator

  20. Herbig-Haro Objects: Stars with Accretion Disks HH30

  21. More Young Stellar Object Jets HH34 HH47

  22. Quasar Jets Cygnus A 3C273

  23. Quadrupole Electric Field: 1st Excited State of a Dipole B-field - - - - - + + + + - - • - -

  24. Can SLAC power jets? • The maximum electric field of such a system is limited by 2nd order forces (F X F X B). Using some typical numbers for YSO for magnetic field strength, we get limiting energies of keV - MeV. • Applying same formula to quasar jets, we get ~1 GeV. Precisely the value that explains observations! • Q: What does a black hole magnetosphere look like???

  25. Conclusions • The Earth’s magnetosphere is a rich & accessible plasma laboratory. • Long range forces of E & B can control plasma and hence astrophysical objects. • Quadrupole cyclotrons are a basic topological feature of B-field + plasma. • Jets occur on many spatial & energy scales, always with accretion disks and magnetic fields. The mechanism must be topological.

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