  We investigate the planar motion of a mass particle in a force field defined
by patching Kepler's and Stark's dynamics. This model is called Sun-shadow
dynamics, referring to the motion of an Earth satellite perturbed by the solar
radiation pressure and considering the Earth shadow effect. The existence of
periodic orbits of brake type is proved, and the Sun-shadow dynamics is
investigated by means of a Poincare'-like map defined by a quantity that is not
conserved along the flow. We also present the results of our numerical
investigations on some properties of the map. Moreover, we construct the
invariant manifolds of the hyperbolic fixed points related to the periodic
orbits of brake type. The global picture of the map shows evidence of regular
and chaotic behaviour.
