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

TL;DR

This paper demonstrates that the fine structures in type III solar radio bursts are caused by moving Langmuir wave clumps in turbulent plasma, enabling new remote diagnostics of plasma conditions.

Contribution

It combines theoretical, simulation, and observational approaches to link fine radio structures with Langmuir wave motion in turbulent solar plasma, expanding diagnostic capabilities.

Findings

Fine structures are caused by moving Langmuir wave clumps

Type III fine structure can diagnose plasma turbulence and temperature

Results match high-resolution radio observations

Abstract

The Sun frequently accelerates near-relativistic electron beams that travel out through the solar corona and interplanetary space. Interacting with their plasma environment, these beams produce type III radio bursts, the brightest astrophysical radio sources seen from the Earth. The formation and motion of type III fine frequency structures is a puzzle but is commonly believed to be related to plasma turbulence in the solar corona and solar wind. Combining a theoretical framework with kinetic simulations and high-resolution radio type III observations using the Low Frequency Array, we quantitatively show that the fine structures are caused by the moving intense clumps of Langmuir waves in a turbulent medium. Our results show how type III fine structure can be used to remotely analyse the intensity and spectrum of compressive density fluctuations, and can infer ambient temperatures in astrophysical plasma, both significantly expanding the current diagnostic potential of solar radio emission.