  We develop further a kinetic theory of strings and derive a transport
equation for a network of cosmic strings with Nambu-Goto evolution,
interactions and background gravitational effects taken into account. We prove
an H-theorem and obtain necessary and sufficient conditions for a thermodynamic
equilibrium. At the lowest order the equilibrium is estimated by the von
Mises-Fisher distributions parametrized by mean directions and dispersions of
the right- and left-moving tangent vectors. Under assumption of a local
equilibrium we derive a complete set of hydrodynamic equations that govern the
evolution of strings on large scales. We also argue that on small scales the
assumption of a local equilibrium would break down, and non-equilibrium steady
states, described by the Sinai-Ruelle-Bowen distributions, should be used
instead.
