Stability of confined radio jets: The role of reflection modes
The linear stability of a confined radio jet is reinvestigated. The roles of both absolute (temporal) and convected (spatial) instability are considered, and it is demonstrated that the two are related through the group velocity. The dispersion relation is analyzed asymptotically for the fundamental and reflection modes. Numerical results are presented for pinching modes. A geometrical interpretation of the modes is presented in terms of the propagation angle and is visualized by contour plots of the pressure perturbation. A confined jet is seen to be an acoustic waveguide that supports a set of self-excited modes. At the resonant wavelength of each reflection mode, the acoustic wave fronts meet the jet boundary at the Mach angle, theta/sub M/ = sin/sup -1/((1+eta/sup 1/2/)/ M), where eta is the ratio of the internal to the external gas density and M is the Mach number of the jet. The connection between these linear modes and the cross-shaped shock patterns which are seen in laboratory jets, and the implication of these calculations for the development of large-scale features in extragalactic radio jets, are discussed.
- Research Organization:
- Jet Propulsion Laboratory, California Institute of Technology
- OSTI ID:
- 5315261
- Journal Information:
- Astrophys. J.; (United States), Vol. 291:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
GALAXIES
PLASMA JETS
DISPERSION RELATIONS
HELMHOLTZ INSTABILITY
OSCILLATION MODES
ANALYTICAL SOLUTION
HYDRODYNAMICS
NUMERICAL SOLUTION
QUASARS
RADIOWAVE RADIATION
SOUND WAVES
SUPERSONIC FLOW
WAVE PROPAGATION
WAVEGUIDES
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
FLUID FLOW
FLUID MECHANICS
INSTABILITY
MECHANICS
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
RADIATIONS
640105* - Astrophysics & Cosmology- Galaxies