We present a heuristic model for the energy spectrum of the one-dimensional
phase turbulence in the steady state of the Kuramoto-Sivashinsky equation.
Our model contains an energy transfer mechanism from low- to high-wave-vec
tor modes. The energy transfer is written as the sum of local and nonlocal
interactions. Our analytical results show good agreement with numerical sim
ulations, particularly for the hump in the energy spectrum, which is mainly
due to the local interactions.