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Particle Acceleration in Relativistic Shock Waves

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Particle Acceleration in Relativistic Shock Waves. Masahiro HOSHINO University of Tokyo. Collaboration with T. Amano, K. Nagata, C. Jaroschek, Y. Takagi. Cosmic Accelerator in Astrophysics. Pulsars & Winds ( g ~ 10 6-7 ) Extragalactic radio source ( g ~ 10)

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Particle Acceleration in Relativistic Shock Waves

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  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

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