TIDAL EVOLUTION OF GLOBULAR-CLUSTERS .2. THE EFFECTS OF GALACTIC TIDAL FIELD AND DIFFUSION

We investigate the tidal evolution of globular clusters subject to various degrees of the internal diffusion process. Our results are as follows: (1) In cases of negligible diffusion, clusters are tidally truncated to the theoretical tidal radius at perigalacticon. (2) There is no apparent orbital phase dependence of the tidal radius for clusters with eccentric orbits. (3) In clusters with moderately short two-body relaxation time scales, diffusion processes significantly modify the structure of the outer regions in such a way that the limiting radius may be comparable to the tidal radius at apogalaction. (4) The Galactic tidal torque induces isotropy in the velocity dispersion of the outer regions of the cluster. For relaxed clusters, the velocity dispersion may be isotropic in the core, anisotropic in the envelope, and isotropic near the limiting radius. (5) Disk shocking is also very efficient for isotropizing the orbits of stars in the outer cluster regions. (6) Stars with direct orbits are less stable, so that prolonged tidal interaction can lead to apparent retrograde rotation in the outer regions of the cluster. For clusters with highly anisotropic velocity dispersion, the tidally induced retrograde rotation effect may be extended into relatively small radii. (7) Stellar evaporation rates induced by a two-body relaxation process may be greatly reduced by the Galactic tidal effects.