Compton Spectrum from Poynting Flux Accelerated e e Plasma.

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Compton Spectrum from Poynting Flux Accelerated
ee- Plasma.

• Shinya Sugiyama(1), Edison Liang(1), Koichi
  Noguchi(1), Hideaki Takabe(2)

1 Rice University 2 Osaka University
Rice AU seminar
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Outline

• Motivation
• Poynting flux accelerator and PIC code including
  Compton effect
• Calculation result
• Conclusion

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Outline

• Motivation

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GRB
Long GRB, Afterglow
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Motivation

• GRBs
• Variety of burst, light curves
• Short GRBs (0.2s lt), Long GRBs (lt 0.2s)
• Afterglow
• Energy 1051 erg
• Cosmological Distance z 1
• Non-Thermal spectrum Synchrotron, Compron
  scattering

Particle acceleration
What is the acceleration mechanism?

• fireball?
• Electromagnetic dominated outflow?

PFA
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Outline

• Motivation

• Poynting flux accelerator and PIC code including
  Compton effect

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Poynting flux accelerator ( PFA)
When a long vacuum EM wave irradiate a plasma
surface, the JxB force accelerates only the
surface particles to the plasma. However,
initialy, the plasmas is in the strong
electromagnetic field, the particles can be
accelerated by the JxB force to ultrarelativistic
energies with a power-law momentum distribution.
We call this mechanism the diamagnetic
relativistic pulse accelerator (DRPA) (1).
plasma
Ultrarelativistic energy
JxB force
Electromagnetic Wave
Electromagnetic Wave

• lead power-law spectrum
• Strong angle dependence

(1) E. Liang et al., Phys. Rev. Lett. 90, 085001
(2003). E. Liang and K. Noguchi, RevMexAA, 23,
43-52 (2005)
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Comptonization and Initial Condition of the
calculation
We calculate the Compton scattering emission from
the Poynting flux acceleration of
electron-positron plasma simulated by the 2 ½
dimensional particle-in-cell(PIC) code.
Initial condition
Z
Photons
X
Sudden deconfinement of ee- plasma with strong
magnetic field
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Equations for PIC simulation

• Basic Equation

• Normalization Element

Compton drag term
Initial Background Magnetic Field
Cyclotron period (time)
Charge-mass ratio (charge, mass)
Gyroradii (length)
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Outline

• Motivation
• Poynting flux accelerator and PIC code including
  Compton effect

• Calculation result

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Initial Parameters
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x-Px Evolution
(E)
DRPA

• The diamagnetic relativistic pulse accelerator
  (DRPA) convert the magnetic energy into the
  kinetic energy of the surface particles in every
  case.

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x-Px Evolution
(A)
Compton Damping
DRPA

• The Comptonization energy loss is effective in
  the later time (A), (C).

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x-Px Evolution
(D)
DRPA

• The acceleration beats the comptonization energy
  loss in every calculation time of (B), (D).
  However, the Compton drag will be effective in
  the later time if long duration simulation.

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Px-Pz Evolution
(A)
(E)
Tow population
Compton Drag
DRPA

• DRPA convert the magnetic energy not only into
  the x-direction but also z-direction kinetic
  energy. Roughly, Pz/Px 0.1
• Tow populations in the case (A), (B), (C), (E).
  The particles on the front of Magnetic Wave are
  Pz/Px 0.1, the particles in the Wave are Pz/Px
  0.2.
• The anisotropic distribution of Pz and Px
  determines the angle dependence of Compton
  Emission.

(D)
DRPA
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Gamma Distribution Evolution
(B)
(A)

• Compton drag is efficient at high energy region

DRPA is more efficient than Compton drag because
of the low photon density
DRPA
Compton Drag
(C)
(D)
DRPA

• Strong Compton drag at high energy region
  because of high photon temperature

• DRPA is more efficient than Compton drag because
  of the strong wave amplitude

Compton Drag
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Compton Spectrum (Angle Dependence)
(A)
(B)

• Strong Angle dependence
• Consistent with GRBs?

• Angle dependence
• Consistent with GRBs?

Compton Drag
(D)
(C)

• Angle Dependence
• High Energy cut off?

• Angle Dependence

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Compton Spectrum Evolution
(A)

• The Compton Spectrum has the angle and time
  dependence.
• The spectrum is harder in the latter time of the
  low angle because of the DRPA.
• The Compton damping is efficient at higher
  energy.

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Compton Spectrum Evolution
(B)

• The Compton Spectrum has the angle and time
  dependence.
• The spectrum is harder in the latter time of the
  low angle because of the DRPA.
• The Compton damping is efficient at higher
  energy.

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Compton Spectrum Evolution
(C)

• The Compton Spectrum has the angle and time
  dependence.
• The spectrum is harder in the latter time of the
  low angle because of the DRPA.
• The Compton damping is efficient at higher
  energy.

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Compton Spectrum Evolution
(D)

• The Compton Spectrum has the angle and time
  dependence.
• The spectrum is harder in the latter time of the
  low angle because of the DRPA.
• The Compton damping is efficient at higher
  energy.

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Angle Dependence E-Peak
(D)
(C)

• E-Peak is weakly angle dependent
• The particles are accelerated even at the end of
  the simulation. (more long duration is needed
• Consistent with GRBs?

• E-Peak is angle dependent
• Consistent with GRBs?

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E-Peak Time Dependence
(B)
(A)

• E-Peak is time dependent
• Compton drag stop the growth of E-Peak
• E-Peak growth rate is different between each
  angles

• E-Peak is time dependent
• The DRPA is more efficient than the Compton
  (more long duration simulation is needed)

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Outline

• Motivation
• Poynting flux accelerator and PIC code including
  Compton effect
• Calculation result

• Conclusion

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Conclusion

• The diamagnetic relativistic pulse accelerator
  (DRPA) convert the magnetic energy into the
  kinetic energy of the surface particles
  effectively, resulting in ultrarelativistic
  particles.
• The Compton drag is effective in the case of high
  density and hot photon surrounding ee- plasmas.
• The large part of particles momentum is
  x-direction, but slightly tilted to z-direction,
  Pz/Px 0.1-0.2.
• The particle momentum distribution is roughly
  at low energy, at high energy.
• The Compton spectrum has strong angle, time
  dependence. We can see the high energy cut off by
  the Compton drag in the Compton efficiency case
  because of the Compton drag .
• We can see the power-law spectrum at high energy
  region of the inefficient Compton drag case. This
  power-law and E-peak might be consistent with
  GRBs or X-ray Flash. However, longer duration
  simulation will be needed to build up the correct
  power-law tail.
• The range of Epk calculated agrees with observed
  classical GRBs.