Thyr: a volumetric ray-marching tool for simulating microwave emission

Osborne, C. M.J. and Simoes, P. J.A. (2019) Thyr: a volumetric ray-marching tool for simulating microwave emission. Monthly Notices of the Royal Astronomical Society, 485(3), pp. 3386-3397. (doi: 10.1093/mnras/stz660)

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Gyrosynchrotron radiation is produced by solar flares, and can be used to infer properties of the accelerated electrons and magnetic field of the flaring region. This microwave emission is highly dependent on many local plasma parameters, and the viewing angle. To correctly interpret observations, detailed simulations of the emission are required. Additionally, gyrosynchrotron emission from the chromosphere has been largely ignored in modelling efforts, and recent studies have shown the importance of thermal emission at millimetric wavelengths. Thyr is a new tool for modelling microwave emission from three-dimensional flaring loops with spatially varying atmosphere and increased resolution in the lower corona and chromosphere. Thyr is modular and open-source, consisting of separate components to compute the thermal and non-thermal microwave emission coefficients and perform three-dimensional radiative transfer (in local thermodynamic equilibrium). The radiative transfer integral is computed by a novel ray-marching technique to efficiently compute the contribution of many volume elements. This technique can also be employed on a variety of astrophysics problems. Herein we present a review of the theory of gyrosynchrotron radiation, and two simulations of identical flare loops in low- and high resolution performed with Thyr, with a spectral imaging analysis of differing regions. The high-resolution simulation presents a spectral hardening at higher frequencies. This hardening originates around the top of the chromosphere due to the strong convergence of the magnetic field, and is not present in previous models due to insufficient resolution. This hardening could be observed with a coordinated flare observation from active radio observatories.

Item Type:Articles
Additional Information:C.M.J.O is grateful for the financial support of the Royal Society of Edinburgh Cormack Undergraduate Vacation Research Scholarship (2016), and the Royal Astronomical Society Undergraduate Summer Bursary (2015) under which this project took shape. C.M.J.O also acknowledges financial support from STFC Doctoral Training Grant ST/R504750/1. P.J.A.S. acknowledges support from the University of Glasgow’s Lord Kelvin Adam Smith Leadership Fellowship. This work builds upon the results obtained from projects funded by FAPESP grants 03/03406-6, 04/14248-5, 08/09339-2 and 2009/18386-7.
Glasgow Author(s) Enlighten ID:Simoes, Dr Paulo and Osborne, Mr Christopher
Authors: Osborne, C. M.J., and Simoes, P. J.A.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Monthly Notices of the Royal Astronomical Society
Publisher:Oxford University Press
ISSN (Online):1365-2966
Published Online:07 March 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Monthly Notices of the Royal Astronomical Society 485(3): 3386-3397
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
3013880STFC Glasgow 2017 DTPMartin HendryScience and Technology Facilities Council (STFC)ST/R504750/1P&S - Physics & Astronomy