Force-free simulations of ultra-relativistic jets

Alexander Tchekhovskoy*, Jonathan C. McKinney, Ramesh Narayan

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


We describe time-dependent axisymmetric numerical simulations of ultrarelativistic highly-magnetized, force-free jets. The simulations follow the jet from the central engine to beyond six orders of magnitude in radius. The simulated jets are confined by an external pressure which we take to vary as a power-law with distance along the jet. We find that the radial distance over which the jet is pressure supported determines the terminal Lorentz factor. For the collapsar model of GRBs, this distance is set by the size of the progenitor star and is very large. At this distance our fiducial model generates a Lorentz factor γ∼400 and a half-opening angle θj∼2°, consistent with observations of many long GRBs. Other models with slightly different parameters give γ in the range 100 to 5000 and θj from 0.1° to 10°, thus reproducing the range of properties inferred for GRB jets. A potentially observable feature of some of our solutions is that both γ and the Poynting flux S are concentrated in hollow cones, with the half-opening angle of the γ-cone θγ≪θj and the half-opening angle of the S-cone θsj. In the case of systems such as AGN, XRBs, and short GRBs, we expect the confining medium, viz., the disk wind, to act over a shorter range of distance. This would explain the lower terminal Lorentz factor of these systems compared to long GRBs.

Original languageEnglish (US)
Title of host publicationCool Discs, Hot Flows
Subtitle of host publicationThe Varying Faces of Accreting Compact Objects
Number of pages7
StatePublished - 2008
EventCool Discs, Hot Flows: The Varying Faces of Accreting Compact Objects - Funasdalen, Sweden
Duration: Mar 25 2008Mar 30 2008

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


OtherCool Discs, Hot Flows: The Varying Faces of Accreting Compact Objects


  • Astrophysical jets
  • Black holes
  • Gamma-ray bursts
  • Plasma magnetohydrodynamics

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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