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Inductive and Electrostatic Acceleration in Relativistic JetPlasma Interactions. Johnny S.T. Ng and Robert J. Noble Stanford Linear Accelerator Center, Stanford University URJA 2005, Banff, Canada July 12, 2005. Motivations. High energy astrophysics phenomenon involve interactions
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Inductive and Electrostatic Acceleration in Relativistic JetPlasma Interactions
Johnny S.T. Ng and Robert J. Noble
Stanford Linear Accelerator Center, Stanford University
URJA 2005, Banff, Canada
July 12, 2005
High energy astrophysics
phenomenon involve interactions
of relativistic (bulk G>>1)plasma
with ambient plasma, for example:
GRB: colliding plasma shells
 AGN jets: bowshocks
Strong nonlinear dynamics can
produce:
highly nonthermal radiation
 particle acceleration – perhaps even
ultrahigh energy cosmic rays.
Suggested in Oct. 2001 Workshop on Laboratory Astrophysics at SLAC:
1. Cline (UCLA): Primordial Black Hole Induced Plasma Instability Expt.
2. Sokolsky (Utah): High Energy Shower Expt. for UHECR SLAC E165
3. Kirkby (CERN): CLOUD Expt. on Climate Variation
4. ChenTajima (SLACAustin): Ponderomotive Acceleration Expt. for UHECR and Blazars
5. Nakajima (KEK): Laser Driven Dirac Acceleration for UHECR Expt.
6. Odian (SLAC): NonAskaryan Effect Expt.
7. Rosner (Chicago): Astro Fluid Dynamics Computer Code Validation Expt.
8. ColgateLi (LANL): Magnetic Flux Transport and Acceleration Expt.
9. Kamae (SLAC): Photon Collider for Cold e+e– Plasma Expt.
10.BegelmanMarshall (COMIT): XRay Iron Spectroscopy and Polarization Effects Expt.
11. Ng (SLAC): Relativistic e+e– Plasma Expt.
12. Katsouleas (USC): BeamPlasma Interaction Induced Photon Burst Expt.
13. Blandford (CalTech): BeamPlasma Filamentation Instability Expt.
14. Scargle (NASAAmes): Relativistic MHD Landau Damping Expt.
Pisin Chen (102201)
[J. Dawson, Rev. Mod. Phys. 55, 403 (1983); Birdsall and Langdon, “Plasma Physics via Computer Simulation”, IOP Publishing Ltd 1991]
Wellsuited to study complex plasma dynamics problems
PIC Code: TRISTAN Package
Recent PIC Simulations of JetPlasma Systems
These studies concentrated on wide jets using periodic
boundary conditions to study the interior dynamics
cause particle acceleration in jetplasma interactions.
interface region of wide jets.
Stability checks:
Simulation geometry: continuous jet.
Jet electrons: gray dots
Jet positrons: black dots
g=10
Simulation geometry: finitelength (10 c/wpe) jet.
Jet electrons: gray dots
Jet positrons: black dots
g=10
B
Streaming Neutral Plasma Systems: Plasma Filamentation
Weibel instability (1959) is the spontaneous filamentation of the jet into separate
currents and the generation of associated azimuthal magnetic fields.
magnetic field perturbation
magnified by filaments
small B field
perturbation
from plasma noise
┴
j

.
.
e
… then
hose, pinch,
streaming
instabilities!
Mass
flow but
je=0
e+
B
+
j
Davidson and Yoon (1987)
Weibel growth time:
Transverse scale size:
Γ = f(β ,βz) ωp(b) /γ1/2
~ (n/γ)1/2
d = g(β ,βz) c/ωp(b)
~ (1/n)1/2
┴
┴
typ. f <1
typ. g >1
Past simulations: Saturated EM energy density/particle KE density ~ 0.01 – 0.1
Illustrative Case: gamma =10, jet/plasma density = 10
∫ E2dV
∫ B2dV
105
105
1/ ωp
E & B
fields
Avg plasma part.KE/mc2
c/ ωp
Jet e+ e density contours
Plasma e density contour
Some Results from this Illustrative Case:
Strong plasma heating
of order mec2
Growth rate:
E2 ~ exp(2Γt) → Γ ≈ 0.85 ωp= 0.85 ωp(b)/γ1/2
105
Log
plot
105
1/ ωp
Linear
plot
1/ ωp
Longitudinal E fields
start building up
once the jet breaks up into
e+ and e filaments
Simulation Results: Overview
Chargeneutral, electronpositron jet interacting with cold
electronion background plasma (not shown)
Correlation of longitudinal electric
field with time variation of azimuthal
magnetic field, in normalized units,
for a finitelength jet.
t in units of 1/wp
Electron
filament
[See P. Chen et al., Phys. Rev. Lett. 54, 693 (1985); talk at this Workshop]
Finitelength, chargeneutral, electronpositron jet interacting with cold electronion
background plasma – development of electric field Ez is shown vs x and z.
Correlation of longitudinal electric
field with time variation of azimuthal
magnetic field, in normalized units,
for a finitelength jet.
Inductive
t in units of 1/wp
Wakefield and Inductive
Wakefield dominant (finitelength jet)
Longitudinal momentum distribution
of positrons and electrons for a
finitelength jet at three simulation
time epochs.
t in units of 1/wp
~ 40% of positrons gained >50%
In longitudinal momentum (pz)
Summary
Outlook
Background
electronion plasma
Energy transfer from relativistic plasma via instabilities: acceleration and radiation
Measure particle spectrum and
radiation properties
Acknowledgement
We appreciate discussions with K.I. Nishikawa, K. Reil, A. Spitkovsky,
and M. Watson. We would also like to thank P. Chen, R. Ruth, and
R. Siemann for their support and encouragement.
Work supported by the U.S. Department of Energy under contract number DEAC0276SF00515.