  Nonlinear radio waves modulate the plasma, scatter on the modulations, and
develop an intermittent power spectrum -- perhaps. Rudiments of theory,
numerical simulations, and qualitative modeling of nonlinear scattering are
presented. Nonlinear radio waves in electron-positron plasma are shown to be
unstable, the instability growth rate is calculated. The long-term outcome of
the instability is studied numerically; an intermittent power spectrum is
found. The frequency coherence scale of the intermittent power spectrum is
interpreted as a measure of the nonlinear scattering screen.
