  We present a "thin shell" model of the interaction of a biconical outflow and
a streaming environment (aligned with the direction of the flow), as well as
numerical (axisymmetric) simulations of such an interaction. A similar
situation, although in a more complex setup, takes place at the head of the
cometary structure of Mira. Thus, for most of the numerical simulations we
explore parameters consistent with the observed bipolar outflow from Mira B.
For these parameters, the interaction is non-radiative, so that a rather broad
jet/streaming environment interaction region is formed. In spite of this, a
reasonable agreement between the thin-shell analytic model and the numerical
simulations is obtained.
