THE PARSEC-SCALE EVOLUTION OF THE SUPERLUMINAL QUASAR-1642+690

We present the results of a 6 cm VLBI monitoring program of the core d ominated, radio loud quasar 1642+690. 3.6 cm VLBI observations are als o presented. The 6 cm observations, carried out in 1986.4, 1988.2, 199 2.2 and 1994.7 confirm that the source is variable, both in morphology and in flux density, its changes reflecting a complicated evolution. We propose a few evolutionary scenarios, and favour the interpretation of the superluminal character of 1642+690, with a flow of superlumina l components ejected from the core at a very similar high apparent spe ed, beta(app) similar to 9, in agreement with the first claim of super luminal motion in this source.