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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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Particle acceleration in relativistic shock waves l.jpg

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 l.jpg

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)


Generic acceleration mechanisms l.jpg

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….


Diffusive shock acceleration l.jpg

Diffusive Shock Acceleration

shock front

Fermi Model

MHD waves

MHD waves

V1

V2

Blandford & Ostriker, 1978

Bell 1978

downstream

upstream


New challenge in particle acceleration l.jpg

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.


Shock numerical experiment l.jpg

Shock Numerical Experiment

Modeling on Collisionless Shock

Particle-in-Cell (PIC) Simulation

Bz

Ey

wall

e+,e-

injection

reflection

108 particles


Relativistic shocks l.jpg

Relativistic Shocks

  • Pair (positron-electron) Plasma Shock

  • Ion and Electron Shock


Relativistic shocks8 l.jpg

Relativistic Shocks

  • Pair (positron-electron) Plasma Shock

    • σ~ 1 (Poynting flux dominated)

    • σ<< 1 (Kinetic flux dominated)

  • Ion and Electron Shock


Shock heating for s 0 1 l.jpg

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


Shock acceleration for s 10 4 l.jpg

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


Shock surfing acceleration l.jpg

Y

Ey

Bz

Bz

positron

X

“Shock Surfing” Acceleration

Sagdeev and Shapiro (1973),

Katsouleas and Dawson (1983)…

Bz

Ey

+charge

“Current Sheet” Shock Surfing

charged

particles

Near the Shock Front

-charge

shock surface

This can provide unlimited acceleration

Hoshino PTP 2001, Nagata 2005


S dependence l.jpg

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


Relativistic shocks13 l.jpg

Relativistic Shocks

  • Pair (positron-electron) Plasma Shock

    • σ~ 1 (Poynting flux dominated)

    • σ<< 1 (Kinetic flux dominated)

  • Ion and Electron Shock


Wakefield acceleration in relativistic shock wave l.jpg

Wakefield Acceleration in Relativistic Shock Wave

upstream(supersonic flow)

downstream(sub-sonic)

Ux,ion

Ux,ele

Bz

(EM,photon)

Ex

(ES,plasmon)

X


Electron energy spectra l.jpg

Downstream

Upstream

Electron Energy Spectra

Accelerated electron energy is more than upstream ion bulk flow energy

emax/e0 > Mi/me (=50)


Wakefield acceleration l.jpg

Wakefield Acceleration

Wakefield (plasmon,

Langmuir Wave)

Electron

Laser Pulse (photon,

Electromagnetic Wave)

Vph ~ c

Tajima & Dawson, PRL 1979


Wakefield acceleration17 l.jpg

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


Slide18 l.jpg

Forward Raman Scattering

(pump)

(w0,k0)

(w2,k2)

(w1,k1)


Maximum energy of electron l.jpg

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


Forward backward wakefield accelerations l.jpg

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


Wakefield acceleration in relativistic shock wave21 l.jpg

Wakefield Acceleration in Relativistic Shock Wave

upstream(supersonic flow)

downstream(sub-sonic)

Ux,ion

Ux,ele

Bz

(EM,photon)

Ex

(ES,plasmon)

X


Slide22 l.jpg

Backward Raman Scattering

Forward Raman

(pump)

(w0,k0)

(w2,k2)

(w1,k1)


Summary l.jpg

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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