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 β 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.

Fine structure of type III solar radio bursts from Langmuir wave motion in turbulent plasma

“…39]. We approximate a dynamic spectrum of fundamental emission from the Langmuir wave spectral energy density assuming a saturation level of plasma emission [40,41,42]. The brightness temperature T T (k, r, t) is found using…”

A Fokker–Planck Framework for Studying the Diffusion of Radio Burst Waves in the Solar Corona

“…However, when v g ≃ C s longitudinal Fermi acceleration (i.e., change in energy) is of the same order of (in fact twice) the angular scattering rate. Such considerations can be extended to turbulence produced by other low-frequency plasma modes such as Alfvén waves which become compressive at small-scales (Schekochihin et al 2009;Bian & Tsiklauri 2009;Lyubchyk et al 2017).…”

Combined Radio and Space-Based Solar Observations: From Techniques to New Results – Preface

“…Anticipating future observations in the subTHz range, Rodger and Labrosse (2017) studied how the ratio of brightness temperatures at two frequencies can be used to estimate the optical thickness and the emission measure for prominences. Highlighting that there is no generally accepted theory that would explain high brightness temperatures in type I storms, Lyubchyk et al (2017) proposed a new model to explain type I solar radio bursts associated with active regions. The model is based on the turbulence of kinetic-scale Alfvén waves that produce an asymmetric plateau in the electron velocity and a high level of Langmuir waves, leading to plasma emission.…”

“…This volume provides a snapshot of the developments and challenges that were discussed during the workshop. This Topical collection covers four sub-topics: i) Solar Radio Emission Modelling (Lyubchyk et al, 2017;Rodger and Labrosse, 2017;Stupishin et al, 2018;Zaitsev and Stepanov, 2017) ii) Solar Flares and Solar Energetic Particles (Anastasiadis et al, 2017;Benz, Battaglia, and Güdel, 2017;Altyntsev et al, 2017) iii) Fine Structures in Solar Radio Emission (Mohan and Oberoi, 2017;Mugundhan, Hariharan, and Ramesh, 2017) iv) Coronal Mass Ejections (Al-Hamadani, Pohjolainen, and Valtonen, 2017;Kumari et al, 2017;Long et al, 2017;Melnik et al, 2018;Miteva, Samwel, and Costa-Duarte, 2018) …”

“…1. Solar Radio Emission Modelling (Lyubchyk et al, 2017;Rodger and Labrosse, 2017;Stupishin et al, 2018;Zaitsev and Stepanov, 2017) 2. Solar Flares and Solar Energetic Particles (Anastasiadis et al, 2017;Benz, Battaglia, and Güdel, 2017;Altyntsev et al, 2017) 3.…”