  We describe the evolution of a bistable chemical reaction in a closed
two-dimensional chaotic laminar flow, from a localized initial disturbance.
When the fluid mixing is sufficiently slow, the disturbance may spread and
eventually occupy the entire fluid domain. By contrast, rapid mixing tends to
dilute the initial state and so extinguish the disturbance. Such a dichotomy is
well known. However, we report here a hitherto apparently unremarked
intermediate case, a persistent highly localized disturbance. Such a localized
state arises when the Damkoehler number is great enough to sustain a hotspot,
but not so great as to lead to global spread. We show that such a disturbance
is located in the neighborhood of an unstable periodic orbit of the flow, and
we describe some limited aspects of its behavior using a reduced, lamellar
model.
