Solar plasma radio emission in the presence of imbalanced turbulence of kinetic-scale Alfvén waves

Abstract

We study the influence of kinetic-scale Alfvénic turbulence on the generation of plasma radio emission in the solar coronal regions where the plasma/magnetic pressure ratio $\beta$ is smaller than the electron/ion mass ratio $m_e/m_i$. The present study is motivated by the phenomenon of solar type I radio storms associated with the strong magnetic field of active regions. The measured brightness temperature of the type I storms can be up to $10^{10}$ K for continuum emission, and can exceed $10^{11}$ K for type I bursts. At present, there is no generally accepted theory explaining such high brightness temperatures and some other properties of the type I storms. We propose the model with the imbalanced turbulence of kinetic-scale Alfvén waves producing an asymmetric quasilinear plateau on the upward half of the electron velocity distribution. The Landau damping of resonant Langmuir waves is suppressed and their amplitudes grow spontaneously above the thermal level. The estimated saturation level of Langmuir waves is high enough to generate observed type I radio emission at the fundamental plasma frequency. Harmonic emission does not appear in our model because the backward-propagating Langmuir waves undergo a strong Landau damping. Our model predicts $100\%$ polarization in the sense of the ordinary (o-) mode of type I emission.

arXiv comment27 pages, 8 figures, accepted for publication in Solar Physics

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Cited by in corpus (6)

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• Fine structure of type III solar radio bursts from Langmuir wave motion in turbulent plasma
• Spatial expansion and speeds of type III electron beam sources in the solar corona
• A Fokker-Planck Framework for Studying the Diffusion of Radio Burst Waves in the Solar Corona
• First observation of the solar Type III burst decay and its interpretation
• Combined Radio and Space-based Solar Observations: From Techniques to New Results