Spatial expansion and speeds of type III electron beam sources in the solar corona

Abstract

A component of space weather, electron beams are routinely accelerated in the solar atmosphere and propagate through interplanetary space. Electron beams interact with Langmuir waves resulting in type III radio bursts. Electron beams expand along the trajectory, and using kinetic simulations, we explore the expansion as the electrons propagate away from the Sun. Specifically, we investigate the front, peak and back of the electron beam in space from derived radio brightness temperatures of fundamental type III emission. The front of the electron beams travelled at speeds from 0.2c--0.7c, significantly faster than the back of the beam that travelled between 0.12c--0.35c. The difference in speed between the front and the back elongates the electron beams in time. The rate of beam elongation has a 0.98 correlation coefficient with the peak velocity; in-line with predictions from type III observations. The inferred speeds of electron beams initially increase close to the acceleration region and then decrease through the solar corona. Larger starting densities and harder initial spectral indices result in longer and faster type III sources. Faster electron beams have higher beam energy densities, produce type IIIs with higher peak brightness temperatures and shorter FWHM durations. Higher background plasma temperatures also increase speeds, particularly at the back of the beam. We show how our predictions of electron beam evolution influences type III bandwidth and drift-rates. Our radial predictions of electron beam speed and expansion can be tested by the upcoming in situ electron beam measurements made by Solar Orbiter and Parker Solar Probe.

19 pages, 20 figures, submitted to ApJ

References in corpus (13)

• A Review of Solar Type III Radio Bursts
• Imaging Spectroscopy of Solar Radio Burst Fine Structures
• Dynamics of electron beams in the solar corona plasma with density fluctuations
• Large scale simulations of solar type III radio bursts: flux density, drift rate, duration and bandwidth
• Dynamics of electron beams in the inhomogeneous solar corona plasma
• Evolution of the Solar Flare Energetic Electrons in the Inhomogeneous Inner Heliosphere
• The Low-High-Low Trend of Type III Radio Burst Starting Frequencies and Solar Flare Hard X-rays
• Solar type III radio burst time characteristics at LOFAR frequencies and the implications for electron beam transport
• Langmuir Wave Electric Fields Induced by Electron Beams in the Heliosphere
• Numerical consideration of quasilinear electron cloud dynamics in plasma
• Coronal type III radio bursts and their X-ray flare and interplanetary type III counterparts
• Small electron acceleration episodes in the solar corona
• Solar plasma radio emission in the presence of imbalanced turbulence of kinetic-scale Alfvén waves

Cited by in corpus (11)

• Fine structure of type III solar radio bursts from Langmuir wave motion in turbulent plasma
• Localised acceleration of energetic particles by a weak shock in the solar corona
• Detection of weak ubiquitous impulsive nonthermal emissions from the solar corona
• Solar Radio Spikes and Type IIIb Striae Manifestations of Sub-second Electron Acceleration Triggered by a Coronal Mass Ejection
• The effects of density inhomogeneities on the radio wave emission in electron beam plasmas
• Properties of Type III and Type IIIb Bursts in the Frequency Band of 8-80 MHz during PSP Perihelion at the Beginning of April 2019
• Solar Type U Burst Associated with a High Coronal Loop
• Wave emission of non-thermal electron beams generated by magnetic reconnection
• First observation of the solar Type III burst decay and its interpretation
• Signatures of Type III Solar Radio Bursts from Nanoflares: Modeling
• Estimating the total energy content in escaping accelerated solar electron beams