Twin beam models for double radio sources. II - Dynamical calculations

Numerical experiments on continuous ejection models for symmetric double radio sources (constructed along the lines of Blandford and Rees (1974)) are performed. The equations for relativistic spherical flow and for nonrelativistic aspherical expansion are derived after a discussion of the physical conditions in both the internal plasma and the confining gas cloud is given. These coupled evolution equations are nondimensionalized, and a scaling law relating configurations of the same reduced luminosities is posited. Models for different values of internal luminosity and for variations in the parameters of the external gas (size, density, temperature, shape) are computed, and the scaling law is verified. The most important variables turn out to be the dimensionless luminosity and the eccentricity of the confining cloud. Low-power models tend to form bubbles: the expanding blob of plasma bifurcates. Stronger sources lead to oppositely directed jets that sometimes attain relativistic expansion velocities. It is also found that the flatter the cloud, the sooner bubbles form.