Volume 625, May 2019
|Number of page(s)||10|
|Published online||13 May 2019|
Comparative analysis of solar radio bursts before and during CME propagation
Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
2 Abastumani Astrophysical Observatory at Ilia State University, Cholokashvili Ave. 3/5, Tbilisi, Georgia
3 Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
4 Combinatorial Optimization and Decision Support, KU Leuven campus Kortrijk, E. Sabbelaan 53, 8500 Kortrijk, Belgium
5 Institute of Radio Astronomy, National Academy of Sciences of Ukraine, Kharkov, Ukraine
6 Poltava Gravimetric Observatory within S.I. Subbotin Institute of Geophysics, Poltava, Ukraine
7 Institute of Physics, IGAM, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
8 Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia
9 Institute of Astronomy of the Russian Academy of Sciences, 119017 Moscow, Russia
Accepted: 19 February 2019
Context. As is well known, coronal mass ejection (CME) propagation often results in the fragmentation of the solar atmosphere on smaller regions of density (magnetic field) enhancement (depletion). It is expected that this type of fragmentation may have radio signatures.
Aims. The general aim of the present paper is to perform a comparative analysis of type III solar and narrow-band type-III-like radio burst properties before and during CME events, respectively. The main goal is to analyze radio observational signatures of the dynamical processes in solar corona. In particular, we aim to perform a comparison of local plasma parameters without and with CME propagation, based on the analysis of decameter radio emission data.
Methods. In order to examine this intuitive expectation, we performed a comparison of usual type III bursts before the CME with narrow-band type-III-like bursts, which are observationally detectable on top of the background type IV radio bursts associated with CME propagation. We focused on the analysis of in total 429 type III and 129 narrow-band type-III-like bursts. We studied their main characteristic parameters such as frequency drift rate, duration, and instantaneous frequency bandwidth using standard statistical methods. Furthermore, we inferred local plasma parameters (e.g., density scale height, emission source radial sizes) using known definitions of frequency drift, duration, and instantaneous frequency bandwidth.
Results. The analysis reveals that the physical parameters of coronal plasma before CMEs considerably differ from those during the propagation of CMEs (the observational periods 2 and 4 with type IV radio bursts associated with CMEs). Local density radial profiles and the characteristic spatial scales of radio emission sources vary with radial distance more drastically during the CME propagation compared to the cases of quasistatic solar atmosphere without CME(s) (observational periods 1 and 3).
Conclusions. The results of the work enable us to distinguish different regimes of plasma state in the solar corona. Our results create a solid perspective from which to develop novel tools for coronal plasma studies using radio dynamic spectra.
Key words: Sun: corona / Sun: radio radiation / Sun: coronal mass ejections (CMEs) / solar wind
© ESO 2019
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