Considering a family of two-dimensional piecewise linear maps, we disc
uss two different mechanisms of reunion of two (or more) pieces of cyc
lic chaotic attractors into a one-piece attracting set, observed in se
veral models. It is shown that, in the case of so-called 'contact bifu
rcation of the 2(nd) kind', the reunion occurs immediately due to homo
clinic bifurcation of some saddle cycle belonging to the basin boundar
y of the attractor. In the case of so-called 'contact bifurcation of t
he 1(st) kind', the reunion is a result of a contact of the attractor
with its basin boundary which is fractal, including the stable set of
a chaotic invariant hyperbolic set appeared after the homoclinic bifur
cation of a saddle cycle on the basin boundary. (C) 1998 Elsevier Scie
nce Ltd. All rights reserved.