RELATIVISTIC RADIATION MEDIATED SHOCKS

Journal Article · Fri Dec 10 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/725/1/63· OSTI ID:21474455

Budnik, Ran; Katz, Boaz; Sagiv, Amir; Waxman, Eli ^[1]

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1. Physics Faculty, Weizmann Institute, Rehovot 76100 (Israel)

The structure of relativistic radiation mediated shocks (RRMSs) propagating into a cold electron-proton plasma is calculated and analyzed. A qualitative discussion of the physics of relativistic and non-relativistic shocks, including order of magnitude estimates for the relevant temperature and length scales, is presented. Detailed numerical solutions are derived for shock Lorentz factors {Gamma}{sub u} in the range 6 {<=} {Gamma}{sub u} {<=} 30, using a novel iteration technique solving the hydrodynamics and radiation transport equations (the protons, electrons, and positrons are argued to be coupled by collective plasma processes and are treated as a fluid). The shock transition (deceleration) region, where the Lorentz factor {Gamma} drops from {Gamma}{sub u} to {approx}1, is characterized by high plasma temperatures T {approx} {Gamma}m{sub e}c {sup 2} and highly anisotropic radiation, with characteristic shock-frame energy of upstream (US) and downstream (DS) going photons of a few x m{sub e}c {sup 2} and {approx}{Gamma}{sup 2} m{sub e}c {sup 2}, respectively. Photon scattering is dominated by e {sup {+-}} pairs, with the pair-to-proton density ratio reaching {approx}10{sup 2{Gamma}}{sub u}. The width of the deceleration region, in terms of Thomson optical depths for US-going photons, is large, {Delta}{tau} {approx} {Gamma}{sup 2}{sub u} ({Delta}{tau} {approx} 1 neglecting the contribution of pairs) due to Klein-Nishina suppression of the scattering cross section. A high-energy photon component, narrowly beamed in the DS direction, with a nearly flat power-law-like spectrum, {nu}I{sub {nu} {proportional_to}} {nu}{sup 0}, and an energy cutoff at {approx}{Gamma}{sup 2}{sub u} m{sub e}c {sup 2} carries a fair fraction of the energy flux at the end of the deceleration region. An approximate analytic model of RRMS, reproducing the main features of the numerical results, is provided.

• OSTI ID: 21474455
• Journal Information: Astrophysical Journal, Vol. 725, Issue 1; Other Information: DOI: 10.1088/0004-637X/725/1/63; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANISOTROPY
APPROXIMATIONS
COSMIC ELECTRONS
COSMIC GAMMA BURSTS
COSMIC PHOTONS
COSMIC POSITRONS
COSMIC PROTONS
CROSS SECTIONS
ELECTRON TEMPERATURE
HYDRODYNAMICS
ION TEMPERATURE
NUMERICAL SOLUTION
PLASMA
PROTON DENSITY
RADIATION TRANSPORT
RELATIVISTIC RANGE
THERMAL SHOCK
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARYONS
BOSONS
CALCULATION METHODS
COSMIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
FLUID MECHANICS
HADRONS
IONIZING RADIATIONS
LEPTONS
MASSLESS PARTICLES
MATHEMATICAL SOLUTIONS
MATTER
MECHANICS
NUCLEONS
PHOTONS
POSITRONS
PRIMARY COSMIC RADIATION
PROTONS
RADIATIONS
SECONDARY COSMIC RADIATION