High Time Resolution Observations of Langmuir Waves Associated with Type III Radio Bursts and Implications for Beam Stabilization and Emission Mechanisms

Type III radio bursts are produced by energetic electron beams accelerated in the solar active regions. As the electron beams propagate out of solar atmosphere, they interact with the ambient plasma, which results in the beam-plasma instability. The growth of this instability leads to intense Langmuir turbulence, which is suspected to be responsible for the stabilization of electron beams, so that they can travel from the inner corona to 1 AU and beyond, as well as for generating the electromagnetic waves at the fundamental and harmonic of the electron plasma frequency, f_pe via nonlinear wave-wave interactions. We report the STEREO and WIND observations of local type III radio bursts and associated Langmuir waves generated in the vicinity of the spacecraft. By analyzing the high time resolution observations of Langmuir waves, we attempt to identify the non-linear wave-wave interactions in the source regions of type III radio bursts. We also examine whether the observed Langmuir wave packets satisfy the characteristics of Langmuir Eigen modes and critically examine the role of these Langmuir Eigen modes in the beam stabilization and conversion of Langmuir waves into escaping radiation at the fundamental and harmonic of the electron plasma frequency.