Study of Solar Radio Emission Mechanisms

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The investigators will develop a quantitative theoretical and numerical analysis of electromagnetic plasma weak turbulence, with the aim of investigating the basic radiation mechanism at the plasma frequency and its harmonics. Such a mechanism, known in the literature as the plasma emission, is accepted as the process responsible for solar type II and type III radio bursts in the corona and interplanetary space. Despite more than 40 years of theoretical research on this topic, however, the basic set of equations have not been quantitatively solved to this date, owing to the enormous complexity associated with obtaining such a solution. In this research program, the basic theory of plasma emission will be reformulated from the most basic set of equations governing the plasma dynamics. Once the electromagnetic effects are fully taken into account, the numerical code will be developed to solve the final set of equations. However, unlike the Langmuir turbulence problem where a one-dimensional approximation reasonably describes the essential physics, the electromagnetic plasma emission problem requires at least a two-dimensional treatment at the outset. The final numerical result is expected to lead to a much better understanding of the plasma emission problem, and help resolve some of the outstanding issues such as the wave growth period, the saturated spectrum, and most importantly, the issue associated with the relative efficiency of the standard three-wave process versus an alternative mechanism which involves the excitation of the so-called nonlinear beam mode. The study may have impacts on other fields, e.g., laser-plasma interaction, microwave generation devices, beam-plasma discharge, rocket active experiments, ionospheric microwave heating experiments, solar and interplanetary radio wave bursts and energetic particles, bow-shock radio waves and energetic particles, and cosmic rays.