  In recent works, we proposed a hypothesis, according to which turbulence in
gases is created by the mean field effect of an intermolecular potential. We
discovered that, in a numerically simulated inertial flow, turbulent solutions
indeed spontaneously emerge from a laminar initial condition, as observed in
nature and experiments. To study the origin of turbulent dynamics, in the
current work we examine the equations of a two-dimensional inertial flow,
linearized around a large scale constant vorticity state. Remarkably, even in
this simplified setting, we find that turbulent dynamics emerge as linearly
unstable fluctuations of the velocity divergence.
  In particular, for the linearized dynamics at a high Reynolds number, we find
that, at short time scales, the coupling of the mean field potential with the
large scale background vorticity creates linearly unstable, rapidly oscillating
fluctuations of the divergence of velocity at inertial scales. In the
asymptotic time limit, we find a persistent eigenvector, also aligned largely
with the divergence of velocity, which allows these fluctuations to propagate
in the form of traveling waves in the Fourier domain. Remarkably, these
traveling waves decay at a constant, scale-independent exponential rate, which
is rather unusual, because all explicitly dissipative terms in the equations
are viscous. Furthermore, it appears that the famous Kolmogorov scaling of the
kinetic energy is produced by this persistent velocity divergence, due to a
cubic relation between the physical time variable, and a pseudo-time variable,
in which the dynamics become asymptotically autonomous. These effects vanish
when the mean field potential is removed.
