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Particle Acceleration in Relativistic Shock WavesPowerPoint Presentation

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)

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

- 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)

〇 shock waves

- diffusive shock acceleration

- direct acceleration

〇 magnetic reconnection

〇 double layer

〇 turbulence

〇 unipolar inductor (e.g. pulsar magnetosphere)

○ etc….

shock front

Fermi Model

MHD waves

MHD waves

V1

V2

Blandford & Ostriker, 1978

Bell 1978

downstream

upstream

- 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.

Modeling on Collisionless Shock

Particle-in-Cell (PIC) Simulation

Bｚ

ｚ

Eｙ

wall

ｙ

e+,e-

ｘ

injection

reflection

108 particles

- Pair (positron-electron) Plasma Shock
- Ion and Electron Shock

- Pair (positron-electron) Plasma Shock
- σ~ 1 (Poynting flux dominated)
- σ<< 1 (Kinetic flux dominated)

- Ion and Electron Shock

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

relativistic Maxwellian

injection

shock front

wall

upstream

downstream

nonthermal particles

- EM waves are very strong
- Strong Acceleration occurs at the shock front

Y

Eｙ

Bｚ

Bｚ

positron

X

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

s=10-1

s=10-2

s=10-4

s=10-3

Nonthermal

σ< 10-3 → strong non-thermal acceleration

σ= 10-2 → marginal

- Pair (positron-electron) Plasma Shock
- σ~ 1 (Poynting flux dominated)
- σ<< 1 (Kinetic flux dominated)

- Ion and Electron Shock

upstream（supersonic flow）

downstream（sub-sonic）

Ux,ion

Ux,ele

Bz

(EM,photon)

Ex

(ES,plasmon)

X

Downstream

Upstream

Accelerated electron energy is more than upstream ion bulk flow energy

emax/e0 > Mi/me (=50)

Wakefield (plasmon,

Langmuir Wave)

Electron

Laser Pulse (photon,

Electromagnetic Wave)

Vph ~ c

Tajima & Dawson, PRL 1979

resonant-acceleration

for electrons

wakefield (vph ~c)

is generated

photon injection from

left-hand boundary

Ux,ion

Ux,ele

Uy,ele

Ex

Nele

Bz

Forward Raman Scattering

(pump)

(w0,k0)

(w2,k2)

(w1,k1)

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 Acceleration,

Same as Laser Wakefield

Ux,ion

Acceleration

toward positive direction

Ux,ele

Bz

Langmuir waves, propagating toward positive direction

Ex

downstream

upstream

upstream（supersonic flow）

downstream（sub-sonic）

Ux,ion

Ux,ele

Bz

(EM,photon)

Ex

(ES,plasmon)

X

Backward Raman Scattering

Forward Raman

(pump)

(w0,k0)

(w2,k2)

(w1,k1)

- 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