1998/02/11 by Abhas Mitra, Mitra, Abhas
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9802125
15 pages Latex using aasms4.sty file and a Postscript Fig., submitted to Astrophy. J. on Janurary 22, 1998
arxiv created 1998/02/11 · arxiv updated 2009/12/01
We point out that the already existing literature on relativistic collisionless MHD shocks show that the parameter sigma= upstream proper magnetic energy density/upstream rest mass energy density, plays an important role in determining the structure and accelerating properties of such shocks. By adopting a value of sigma= 0.002 which corresponds to the relativistic shock associated with the Crab nebula, and by using appropriate relativistic shock jump conditions, we obtain here a generous upper-limit on the value of (proper) the magnetic field, B ~ 1.5 10-3 eta n1/2 G, for gamma ray burst (GRB) blast wave. Here, eta= E/Mc2, where E is the energy and M is the mass of the baryons entrained in the original fireball (FB), and n is the proper number density of the ambient medium. Further, we point out that, in realistic cases, the actual value B could be as low as 5 10-6 eta n1/2 G. for realistic cases.