Book contents
- Frontmatter
- Contents
- Foreword
- Preface
- Notation
- Quotation acknowledgements
- 1 A zoo of astrophysical transient sources
- 2 Electromagnetic radiation processes
- 3 Curved spacetime and gravitational waves
- 4 Hadronic processes and neutrino emissions
- 5 Relativistic fluid dynamics
- 6 Winds and jets
- 7 Relativistic shock waves
- 8 Relativistic blast waves
- 9 Accretion disks and tori
- 10 Entropic attraction in black hole binaries
- 11 Transient sources from rotating black holes
- 12 Searching for long bursts in gravitational waves
- 13 Epilogue: the multimessenger Transient Universe
- Appendix A Some properties of Kerr black holes
- Appendix B Cosmological event rates
- Appendix C Relaxation limited evaporation
- Appendix D Some units and constants
- References
- Index
6 - Winds and jets
Published online by Cambridge University Press: 05 August 2012
- Frontmatter
- Contents
- Foreword
- Preface
- Notation
- Quotation acknowledgements
- 1 A zoo of astrophysical transient sources
- 2 Electromagnetic radiation processes
- 3 Curved spacetime and gravitational waves
- 4 Hadronic processes and neutrino emissions
- 5 Relativistic fluid dynamics
- 6 Winds and jets
- 7 Relativistic shock waves
- 8 Relativistic blast waves
- 9 Accretion disks and tori
- 10 Entropic attraction in black hole binaries
- 11 Transient sources from rotating black holes
- 12 Searching for long bursts in gravitational waves
- 13 Epilogue: the multimessenger Transient Universe
- Appendix A Some properties of Kerr black holes
- Appendix B Cosmological event rates
- Appendix C Relaxation limited evaporation
- Appendix D Some units and constants
- References
- Index
Summary
The virtues, like the Muses, are always seen in groups. A good principle was never found solitary in any breast.
Guatama Buddha (d.o.b. c.486 BC)In this chapter we shall develop fundamental concepts for describing relativistic astrophysical outflows. In order for a flow to be accelerated to high Lorentz factors the internal energy per baryon at the flow injection point must largely exceed unity. This internal energy may have a thermal origin as, e.g., in hydrodynamical fireball models, or a magnetic origin, as in pulsar winds and outflows from rotating black holes. A basic question in the former case is how to avoid excessive mass loading. A key issue in the latter case is the conversion of magnetic energy to kinetic energy. Observations seem to indicate that collimation is a generic feature of astrophysical outflows, suggesting that confinement by the ambient medium may play an important role in the dynamics of the system. In the following only steady flows will be considered, for which simple analytic solutions can be obtained.
Hydrodynamic fireballs
Let us consider first an unmagnetized spherical wind. In general, the wind may consist of a mixture of baryons, radiation and electron–positron plasma, which in sufficiently compact regions can be taken to be in local equilibrium. The flow is then characterized by the proper baryon density nb, pressure p, temperature T and velocity uμ = (γ, γv). We further assume that the flow is adiabatic and not subject to any external forces, including gravity (the effect of gravity will be considered in the following sections).
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- Relativistic Astrophysics of the Transient UniverseGravitation, Hydrodynamics and Radiation, pp. 135 - 152Publisher: Cambridge University PressPrint publication year: 2012