Large-scale simulations of solar type III radio bursts: flux density, drift rate, duration, and bandwidth

¹ Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, CV4 7AL, UK
e-mail: h.ratcliffe@warwick.ac.uk
² SUPA School of Physics & Astronomy, University of Glasgow, G12 8QQ, UK

Received: 28 February 2014
Accepted: 22 October 2014

Abstract

Non-thermal electrons accelerated in the solar corona can produce intense coherent radio emission, known as solar type III radio bursts. This intense radio emission is often observed from hundreds of MHz in the corona down to the tens of kHz range in interplanetary space. It involves a chain of physical processes from the generation of Langmuir waves to non-linear processes of wave-wave interaction. We develop a self-consistent model to calculate radio emission from a non-thermal electron population over a large frequency range, including the effects of electron transport, Langmuir wave-electron interaction, the evolution of Langmuir waves due to non-linear wave-wave interactions, Langmuir wave conversion into electromagnetic emission, and finally escape of the electromagnetic waves. For the first time we simulate escaping radio emission over a broad frequency range from 500 MHz down to a few MHz and infer key properties of the radio emission observed: the onset (starting) frequency, identification as fundamental or harmonic emission, peak flux density, instantaneous frequency bandwidth, and timescales for rise and decay. By comparing these large-scale simulations with the observations, we can identify the processes governing the major type III solar radio burst characteristics.