LOFAR observations of fine spectral structure dynamics in type IIIb radio bursts

Sharykin, I.N., Kontar, E.P. and Kuznetsov, A.A. (2018) LOFAR observations of fine spectral structure dynamics in type IIIb radio bursts. Solar Physics, 293(8), 115. (doi:10.1007/s11207-018-1333-2)

169035.pdf - Accepted Version



Solar radio emission features a large number of fine structures demonstrating great variability in frequency and time. We present spatially resolved spectral radio observations of type IIIb bursts in the 30 – 80 MHz range made by the Low Frequency Array (LOFAR). The bursts show well-defined fine frequency structuring called “stria” bursts. The spatial characteristics of the stria sources are determined by the propagation effects of radio waves; their movement and expansion speeds are in the range of (0.1--0.6)c. Analysis of the dynamic spectra reveals that both the spectral bandwidth and the frequency drift rate of the striae increase with an increase of their central frequency. The striae bandwidths are in the range of ≈(20--100) kHz and the striae drift rates vary from zero to ≈0.3 MHzs−1. The observed spectral characteristics of the stria bursts are consistent with the model involving modulation of the type III burst emission mechanism by small-amplitude fluctuations of the plasma density along the electron beam path. We estimate that the relative amplitude of the density fluctuations is of Δn/n∼10−3, their characteristic length scale is less than 1000 km, and the characteristic propagation speed is in the range of 400--800 kms−1. These parameters indicate that the observed fine spectral structures could be produced by propagating magnetohydrodynamic waves.

Item Type:Articles
Keywords:Space and planetary science, astronomy and astrophysics.
Glasgow Author(s) Enlighten ID:Kontar, Professor Eduard
Authors: Sharykin, I.N., Kontar, E.P., and Kuznetsov, A.A.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Solar Physics
ISSN (Online):1573-093X
Published Online:03 August 2018
Copyright Holders:Copyright © 2018 Springer Nature B.V.
First Published:First published in Solar Physics 293(8):115
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
Related URLs:

University Staff: Request a correction | Enlighten Editors: Update this record

Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
728901Consolidated Grant in Solar PhysicsLyndsay FletcherScience & Technology Facilities Council (STFC)ST/P000533/1S&E P&A - PHYSICS & ASTRONOMY