Anisotropic radio-wave scattering and the interpretation of solar radio emission observations

Kontar, E. P. , Chen, X. , Chrysaphi, N. , Jeffrey, N. L.S. , Emslie, A. G., Krupar, V., Maksimovic, M., Gordovskyy, M. and Browning, P. K. (2019) Anisotropic radio-wave scattering and the interpretation of solar radio emission observations. Astrophysical Journal, 884(2), 122. (doi: 10.3847/1538-4357/ab40bb)

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American Astronomical Society logo iop-2016.png A publishing partnership Anisotropic Radio-wave Scattering and the Interpretation of Solar Radio Emission Observations Eduard P. Kontar1, Xingyao Chen1,2, Nicolina Chrysaphi1, Natasha L. S. Jeffrey1,3, A. Gordon Emslie4, Vratislav Krupar5,6, Milan Maksimovic7, Mykola Gordovskyy8, and Philippa K. Browning9 Published 2019 October 17 • © 2019. The American Astronomical Society. All rights reserved. The Astrophysical Journal, Volume 884, Number 2 DownloadArticle PDF DownloadArticle ePub Figures References 206 Total downloads 11 citation on Dimensions. Turn on MathJax Get permission to re-use this article Share this article Share this content via email Share on Facebook Share on Twitter Share on Google+ Share on Mendeley Article information Abstract The observed properties (i.e., source size, source position, time duration, and decay time) of solar radio emission produced through plasma processes near the local plasma frequency, and hence the interpretation of solar radio bursts, are strongly influenced by propagation effects in the inhomogeneous turbulent solar corona. In this work, a 3D stochastic description of the propagation process is presented, based on the Fokker–Planck and Langevin equations of radio-wave transport in a medium containing anisotropic electron density fluctuations. Using a numerical treatment based on this model, we investigate the characteristic source sizes and burst decay times for Type III solar radio bursts. Comparison of the simulations with the observations of solar radio bursts shows that predominantly perpendicular density fluctuations in the solar corona are required, with an anisotropy factor of ~0.3 for sources observed at around 30 MHz. The simulations also demonstrate that the photons are isotropized near the region of primary emission, but the waves are then focused by large-scale refraction, leading to plasma radio emission directivity that is characterized by a half width at half maximum of about 40° near 30 MHz. The results are applicable to various solar radio bursts produced via plasma emission.

Item Type:Articles
Additional Information:A.G.E. was supported by grant NNX17AI16G from NASA's Heliophysics Supporting Research program. V.K. acknowledges support by an appointment to the NASA postdoctoral program at the NASA Goddard Space Flight Center administered by Universities Space Research Association under contract with NASA and the Czech Science Foundation grant 17-06818Y. We also acknowledge support from the International Space Science Institute for the LOFAR and solar flare teams.
Glasgow Author(s) Enlighten ID:Kontar, Professor Eduard and Jeffrey, Dr Natasha and Chrysaphi, Dr Nicolina and Chen, Dr Xingyao
Authors: Kontar, E. P., Chen, X., Chrysaphi, N., Jeffrey, N. L.S., Emslie, A. G., Krupar, V., Maksimovic, M., Gordovskyy, M., and Browning, P. K.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:American Astronomical Society
ISSN (Online):1538-4357
Published Online:17 October 2019
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
173869Consolidated Grant in Solar PhysicsLyndsay FletcherScience and Technology Facilities Council (STFC)ST/P000533/1P&S - Physics & Astronomy