Propagation of energetic electrons from the corona into interplanetary space and type III radio emission

TL;DR

This paper investigates how energetic electrons from solar flares propagate through the corona into interplanetary space and generate type III radio bursts, using a new heliospheric density model to analyze their velocities.

Contribution

It introduces a new density model of the heliosphere to derive electron propagation velocities from radio burst drift rates.

Findings

Radio emission is produced by electrons with varying radial velocities.

Type III bursts originate from different electrons within the initial electron distribution.

The new density model improves understanding of electron propagation in the heliosphere.

Abstract

During solar flares a large amount of electrons with energies greater than 20 keV is generated with a production rate of typically $10^{36}$ s$^{-1}$. A part of them is able to propagate along open magnetic field lines through the corona into interplanetary space. During their travel they emit radio radiation which is observed as type III radio bursts in the frequency range from 100 MHz down to 10 kHz by the WAVES radio spectrometer aboard the spacecraft WIND, for instance. From the drift rates of these bursts in dynamic radio spectra the radial propagation velocity $V_r$ of the type III burst exciting electrons is derived by employing a newly developed density model of the heliosphere. Calculations show that the radio radiation is emitted by electrons with different $V_r$ and therefore by different electrons of the initially produced electron distribution.