1. Particle Acceleration at a Blunt Termination Shock Nathan Schwadron (BU) Marty Lee ( UNH) Dave McComas (SwRI) 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, ‘93 Chalov, ‘05

7. Injection at a Blunt Termination Shock

8. Simple Model with Blunt TS

9. 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  BN 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