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Particle Acceleration at a Blunt Termination Shock Nathan Schwadron (BU) Marty Lee ( UNH)

Particle Acceleration at a Blunt Termination Shock Nathan Schwadron (BU) Marty Lee ( UNH) Dave McComas (SwRI). Voyager 1 Reaches the TS – December 2004. Shocking ACR Spectra Outside TS. Stone et al., 2005.

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Particle Acceleration at a Blunt Termination Shock Nathan Schwadron (BU) Marty Lee ( UNH)

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  1. Particle Acceleration at a Blunt Termination Shock Nathan Schwadron (BU) Marty Lee (UNH) Dave McComas (SwRI)

  2. Voyager 1 Reaches the TS – December 2004

  3. Shocking ACR Spectra Outside TS • Stone et al., 2005 • Unexpected when the ACRs observed by V1 did not peak at the TS as had been so widely predicted • Continued to see the characteristic ACR “bump” at ~100 MeV caused by modulation

  4. The Voyager ACR Paradox • V1 Proved that ACRs were not being accelerated by the TS at the time and location where it passed through • So where and how are they accelerated? • Are ACRs generated only at special, favored acceleration regions on the shock? • Are they accelerated only at some times at any given shock location? • Are we completely wrong and ACRs are accelerated by some other means at some location further out, beyond the termination shock (e.g., Gloeckler and Fisk)? • Clearly show how little we really know about our local cosmic accelerator • Local observations beg the question of the global interaction

  5. Magnetic Geometry at a Blunt TS • TS shape taken from Zank, 1999

  6. Injection Problem Chalov, ‘05 Chalov, ‘93

  7. Injection at a Blunt Termination Shock

  8. Simple Model with Blunt TS

  9. Diffusive Drift Acceleration

  10. Diffusive Drift Acceleration

  11. Correlated ACRs & GCRs • Strong correlation shows GCRs and ACRs are moving to the nose from much farther out in the heliosheath

  12. Summary • Shape Matters !!! • Always knew that TS was blunt and not spherical, but didn’t appreciate that the TS shape drives the macro-interaction • Many sketches, drawings, and even some simulations • Explained precursor event anisotropies inside TS (Jokipii et al., 2004) • Flattening of the nose of the TS produces a macro-scale geometry that enables a simple, standard time-dependent acceleration of ACRs • Smaller θBN and lower injection energies away from nose • Higher energy particles generated on flanks where magnetic field lines have pierced the TS for longer times • Real spectra vs location will depend on actual TS shape and detailed interactions

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