Particle Acceleration in Relativistic Shock Waves

1. Particle Acceleration in Relativistic Shock Waves Masahiro HOSHINO University of Tokyo Collaboration with T. Amano, K. Nagata, C. Jaroschek, Y. Takagi

2. Cosmic Accelerator in Astrophysics • Pulsars & Winds (g ~ 106-7) • Extragalactic radio source (g ~ 10) • Gamma ray bursts (g > 100) • Sources for UHE CR? Crab Nebula GRB model AGN jet (M87)

3. Generic Acceleration Mechanisms 〇 shock waves - diffusive shock acceleration - direct acceleration 〇 magnetic reconnection 〇 double layer 〇 turbulence 〇 unipolar inductor (e.g. pulsar magnetosphere) ○ etc….

4. Diffusive Shock Acceleration shock front Fermi Model MHD waves MHD waves V1 V2 Blandford & Ostriker, 1978 Bell 1978 downstream upstream

5. New Challenge in Particle Acceleration • Diffusive shock acceleration is one of possible models, but slow process… • Let us find something else in kinetic plasma processes with fast acceleration(direct acceleration mechanisms) • Surfing Acceleration (e.g. Sagdeev & Shapiro, 1973) • Wakefield Acceleration (e.g., Tajima & Dawson, 1979) • etc.

6. Shock Numerical Experiment Modeling on Collisionless Shock Particle-in-Cell (PIC) Simulation Bｚ ｚ Eｙ wall ｙ e+,e- ｘ injection reflection 108 particles

7. Relativistic Shocks • Pair (positron-electron) Plasma Shock • Ion and Electron Shock

8. Relativistic Shocks • Pair (positron-electron) Plasma Shock • σ~ 1 (Poynting flux dominated) • σ<< 1 (Kinetic flux dominated) • Ion and Electron Shock

9. Shock Heating for s=0.1 injection shock front relativistic Maxwellian wall upstream downstream ・EM waves are strong ・No nonthermal Acceleration Langdon et al. PRL 1988, Gallant et al. ApJ 1992

10. Shock Acceleration for s=10-4 relativistic Maxwellian injection shock front wall upstream downstream nonthermal particles • EM waves are very strong • Strong Acceleration occurs at the shock front

11. Y Eｙ Bｚ Bｚ positron X “Shock Surfing” Acceleration ｚ Sagdeev and Shapiro (1973), Katsouleas and Dawson (1983)… ｙ Bｚ Eｙ ③ +charge “Current Sheet” Shock Surfing ① charged particles ② Near the Shock Front ｘ ③ -charge shock surface This can provide unlimited acceleration Hoshino PTP 2001, Nagata 2005

12. s dependence s=10-1 s=10-2 s=10-4 s=10-3 Nonthermal σ< 10-3 → strong non-thermal acceleration σ= 10-2 → marginal

13. Relativistic Shocks • Pair (positron-electron) Plasma Shock • σ~ 1 (Poynting flux dominated) • σ<< 1 (Kinetic flux dominated) • Ion and Electron Shock

14. Wakefield Acceleration in Relativistic Shock Wave upstream（supersonic flow） downstream（sub-sonic） Ux,ion Ux,ele Bz (EM,photon) Ex (ES,plasmon) X

15. Downstream Upstream Electron Energy Spectra Accelerated electron energy is more than upstream ion bulk flow energy emax/e0 > Mi/me (=50)

16. Wakefield Acceleration Wakefield (plasmon, Langmuir Wave) Electron Laser Pulse (photon, Electromagnetic Wave) Vph ~ c Tajima & Dawson, PRL 1979

17. resonant-acceleration for electrons wakefield (vph ~c) is generated photon injection from left-hand boundary Wakefield Acceleration Ux,ion Ux,ele Uy,ele Ex Nele Bz

18. Forward Raman Scattering (pump) (w0,k0) (w2,k2) (w1,k1)

19. Maximum Energy of Electron Resonance under a traveling potential t=t3 Phase Speed Wakefield t=t2 t=t1 c/wp Maximum Energy of Electrons Maximum Amplitude of Wakefield

20. Forward Acceleration, Same as Laser Wakefield Ux,ion Acceleration toward positive direction Ux,ele Bz Langmuir waves, propagating toward positive direction Ex Forward & Backward Wakefield Accelerations downstream upstream

21. Wakefield Acceleration in Relativistic Shock Wave upstream（supersonic flow） downstream（sub-sonic） Ux,ion Ux,ele Bz (EM,photon) Ex (ES,plasmon) X

22. Backward Raman Scattering Forward Raman (pump) (w0,k0) (w2,k2) (w1,k1)

23. Summary • Pair Plasma (Electron-Positron) Shock • Thermal Plasmas for σ~1 • Nonthermal Particle for σ << 1 by Surfing Acceleration (2) Ion-Electron Shock - Nonthermal Electrons by Wakefield Acceleration