Sizes and shapes of sources in solar metric radio bursts

Gordovskyy, M., Kontar, E. P. , Clarkson, D. L., Chrysaphi, N. and Browning, P. K. (2022) Sizes and shapes of sources in solar metric radio bursts. Astrophysical Journal, 925(2), 140. (doi: 10.3847/1538-4357/ac3bb7)

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Metric and decametric radio-emissions from the Sun are the only direct source of information about the dynamics of non-thermal electrons in the upper corona. In addition, the combination of spectral and imaging (sizes, shapes, and positions) observations of low-frequency radio sources can be used as a unique diagnostic tool to probe plasma turbulence in the solar corona and inner heliosphere. The geometry of the low-frequency sources and its variation with frequency are still not understood, primarily due to the relatively low spatial resolution available for solar observations. Here we report the first detailed multi-frequency analysis of the sizes of solar radio sources observed by the Low-Frequency Array (LOFAR). Furthermore, we investigate the source shapes by approximating the derived intensity distributions using 2D Gaussian profiles with elliptical half-maximum contours. These measurements have been made possible by a novel empirical method for evaluating the instrumental and ionospheric effects on radio maps based on known source observations. The obtained deconvolved sizes of the sources are found to be smaller than previous estimations, and often show higher ellipticity. The sizes and ellipticities of the sources inferred using 2D Gaussian approximation, and their variation with frequency are consistent with models of anisotropic radio-wave scattering in the solar corona.

Item Type:Articles
Additional Information:M.G. and P.K.B. were supported by the Science and Technology Facilities Council (STFC, UK), grant ST/ T00035X/1. D.L.C. and E.P.K. are thankful to DSTL for the funding through the UK-France PhD Scheme (contract DSTLX- 1000106007). E.P.K. was supported by STFC consolidated grant ST/P000533/1. N.C. thanks CNES for its financial support. The authors acknowledge the support by the international team grant ( from ISSI Bern, Switzerland. This paper is based (in part) on data obtained from facilities of the International LOFAR Telescope (ILT) under project code LC3_012, LC4_016, and LC8_027. LOFAR van Haarlem et al. 2013 is the Low Frequency Array designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, which are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d’Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; STFC, UK; Ministry of Science and Higher Education, Poland.
Glasgow Author(s) Enlighten ID:Chrysaphi, Dr Nicolina and Kontar, Professor Eduard and Clarkson, Daniel
Authors: Gordovskyy, M., Kontar, E. P., Clarkson, D. L., Chrysaphi, N., and Browning, P. K.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:IOP Publishing
ISSN (Online):1538-4357
Copyright Holders:Copyright © 2022 The Authors
First Published:First published in Astrophysical Journal 925(2):140
Publisher Policy:Reproduced under a Creative Commons License
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
306515PHAS A&A Group STFC ConsolidatedLyndsay FletcherScience and Technology Facilities Council (STFC)ST/T000422/1P&S - Physics & Astronomy
173869Consolidated Grant in Solar PhysicsLyndsay FletcherScience and Technology Facilities Council (STFC)ST/P000533/1P&S - Physics & Astronomy