  We have found that in two-dimensional Kolmogorov flow a single
spatially-localized turbulence (SLT) exists stably and travels with a constant
speed on average switching the moving direction randomly and intermittently for
moderate values of control parameters: Reynolds number and the flow rate. We
define the coarse-grained position and velocity of an SLT and separate the
motion of the SLT from its internal turbulent dynamics by introducing a
co-moving frame. The switching process of an SLT represented by the
coarse-grained velocity seems to be a random telegraph signal. Focusing on the
asymmetry of the internal turbulence we introduce two coarse-grained variables
characterizing the internal dynamics. These quantities follow the switching
process reasonably. This suggests that the twin attracting invariant sets each
of which corresponds to a one-way traveling SLT are embedded in the attractor
of the moving SLT and the connection of the two sets is too complicated to be
represented by a few degrees of freedom but the motion of an SLT is controlled
by the internal turbulent dynamics.
