A1 Refereed original research article in a scientific journal
Modelling gyrosynchrotron emission from coronal energetic electrons in a CME flux rope
Authors: Husidic, E.; Wijsen, N.; Jebaraj, Immanuel C.; Vourlidas, A.; Linan, L.; Vainio, Rami; Poedts, S.
Publisher: EDP Sciences
Publication year: 2025
Journal:: Astronomy and Astrophysics
Article number: A53
Volume: 701
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202555534
Web address : https://doi.org/10.1051/0004-6361/202555534
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/500443393
Context. Solar flares and coronal mass ejections (CMEs) can accelerate electrons, causing bursts such as type IV emissions in the solar radio continuum. Although radio spectroscopy is a powerful diagnostic tool for the corona, the origin and mechanisms of type IV bursts remain uncertain. In situ measurements can occasionally shed some light on these mechanisms, but they are limited in space and time. Sophisticated numerical modelling offers the best approach to improve our understanding of the physical processes underlying particle dynamics and radio emission. Aims. This research examines type IV radio bursts, exploring the effects of various electron distribution properties and CMEs on their generation and characteristics. To transcend idealised assumptions, we employed realistic anisotropic electron distributions - obtained from particle transport simulations within complex magnetohydrodynamic (MHD) environments - as input for radio emission models. Methods. We used the three-dimensional coronal MHD model COCONUT to generate coronal background configurations, including a CME modelled as an unstable modified Titov-D & eacute;moulin magnetic flux rope (MFR). These MHD simulations were used by the PARADISE particle transport code, which injects energetic electrons into the MFR and tracks their evolution. Finally, we fed the electron distributions and solar wind parameters into the Ultimate Fast Gyrosynchrotron Codes to compute radio emission along lines of sight. Results. Electrons injected close to the flux rope's central axis remained largely confined, producing a gyrosynchrotron emission spectrum resembling observed type IV characteristics. Varying observer positions, CME properties, and spectral indices of the electron energy distributions modified the intensities and durations of the observed bursts. The strongest gyrosynchrotron emission was observed as originating from the CME flanks. Conclusions. Our results indicate that gyrosynchrotron emission is the major component in type IV spectra, although additional contributors cannot be ruled out.
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We thank the anonymous referee for their valuable comments, which helped improve the clarity and rigour of the manuscript. Computational resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government - department EWI. E.H. is grateful to the Space Weather Awareness Training Network (SWATNet) funded by the European Union's Horizon 2020 research and innovation program under the Marie Sk & lstrok;odowska-Curie grant agreement No. 955620. N.W. acknowledges funding from the KU Leuven project 3E241013. I.C.J. is grateful for support by the Research Council of Finland (SHOCKSEE, grant No. 346902, and X-Scale, grant No. 371569), and the European Union's (E.U's) Horizon 2020 research and innovation program under grant agreement No. 101134999 (SOLER). A.V. is supported by NASA grant 80NSSC21K1860. S.P. is funded by the European Union. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or ERCEA. Neither the European Union nor the granting authority can be held responsible for them. This project (Open SESAME) has received funding under the Horizon Europe programme (ERC-AdG agreement No 101141362). These results were also obtained in the framework of the projects C16/24/010 C1 project Internal Funds KU Leuven), G0B5823N and G002523N (WEAVE) (FWO-Vlaanderen), and 4000145223 (SIDC Data Exploitation (SIDEX2), ESA Prodex).
