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The self-consistent evolution of Langmuir turbulence generated by electron beams in solar wind plasmas with density inhomogeneities is calculated by numerical simulations based on a 1D Hamiltonian model. It is shown, owing to numerical simulations performed with parameters relevant to type III solar bursts' conditions at 1 AU, that the presence of long-wavelength random density fluctuations of suffciently large average level crucially modifies the well-known process of beam interaction with Langmuir waves in homogeneous plasmas. [ABSTRACT FROM AUTHOR]

Langmuir wave decay in solar wind plasmas typical of type III bursts' source regions near 1 AU have been reported by several spacecraft observations. In such plasmas, due to the presence of random density fluctuations, wave decay occurs usually simultaneously and compete with other coupling effects between the fields and the density irregularities, as reflection, scattering and/or refraction processes. Numerical simulations show that resonant three-wave coupling processes including several cascades of Langmuir wave decay can occur in such plasmas, leading to wave energy transfer to smaller wavenumbers k, as shown in the frame of weak turbulence theory. However, in such conditions, and contrary to what occurs in homogeneous plasmas, the decay process is localized in space at a given time. Moreover, wave-wave coupling plays a significant role in the modulation of the Langmuir waveforms, in agreement with recent space observations. [ABSTRACT FROM AUTHOR]