We investigate the hydrodynamic stability of a relativistic flow of magnetized plasma in the simplest case where the energy density of the electromagnetic fields is much greater than the energy density of the matter (including the rest mass energy). This is the force-free approximation. We consider the case of a light cylindrical jet in cold and dense environment, so the jet boundary remains at rest. Numerical calculations show that in the force-free approximation, the electron-positron jet with uniform poloidal magnetic field is stable for all velocities of longitudinal motion and rotation. The dispersion curves w = w(k||) have a minimum for k||o ~= 1/R (R is the jet radius). This results in accumulation of perturbations inside the jet with wavelength of the order of the jet radius. The wave crests of the perturbation pattern formed in such a way move along the jet with the velocity exceeding light speed. If one has relativistic electrons emitting synchrotron radiation inside the jet, then this pattern will be visible. This provides us with a new type of superluminal source. If the jet is oriented close to the line of sight, then the observer will see knots moving backward to the core.
The XXVIIth Young European Radio Astronomers Conference
- Pub Date:
- March 1995