Variable emission mechanism of a Type IV radio burst

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Morosan , D E , Kilpua , E K J , Carley , E P & Monstein , C 2019 , ' Variable emission mechanism of a Type IV radio burst ' , Astronomy & Astrophysics , vol. 623 , A63 . https://doi.org/10.1051/0004-6361/201834510

Title: Variable emission mechanism of a Type IV radio burst
Author: Morosan, D. E.; Kilpua, E. K. J.; Carley, E. P.; Monstein, C.
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2019-03-07
Language: eng
Number of pages: 11
Belongs to series: Astronomy & Astrophysics
ISSN: 1432-0746
URI: http://hdl.handle.net/10138/307408
Abstract: Context. The Sun is an active star and the source of the largest explosions in the solar system, such as flares and coronal mass ejections (CMEs). Flares and CMEs are powerful particle accelerators that can generate radio emission through various emission mechanisms. Aims. CMEs are often accompanied by Type IV radio bursts that are observed as continuum emission in dynamic spectra at decimetric and metric wavelengths, but their emission mechanism can vary from event to event. Here, we aim to determine the emission mechanism of a complex Type IV burst that accompanied the flare and CME on 22 September 2011. Methods. We used radio imaging from the Nancay Radioheliograph, spectroscopic data from the e-Callisto network, ARTEMIS, Ondrejov, and Phoenix3 spectrometers combined with extreme-ultraviolet observations from NASA's Solar Dynamic Observatory to analyse the Type IV radio burst and determine its emission mechanism. Results. We show that the emission mechanism of the Type IV radio burst changes over time. We identified two components in the Type IV radio burst: an earlier stationary Type IV showing gyro-synchrotron behaviour, and a later moving Type IV burst covering the same frequency band. This second component has a coherent emission mechanism. Fundamental plasma emission and the electron-cyclotron maser emission are further investigated as possible emission mechanisms for the generation of the moving Type IV burst. Conclusions. Type IV bursts are therefore complex radio bursts, where multiple emission mechanisms can contribute to the generation of the wide-band continuum observed in dynamic spectra. Imaging spectroscopy over a wide frequency band is necessary to determine the emission mechanisms of Type IV bursts that are observed in dynamic spectra.
Subject: Sun: corona
Sun: radio radiation
Sun: particle emission
Sun: coronal mass ejections (CMEs)
CORONAL MASS EJECTION
GUIDE FIELD
SOLAR
RADIATION
ACCELERATION
SYNCHROTRON
SPECTRA
115 Astronomy, Space science
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