Detection of spike-like structures near the front of type-II bursts

Aims. We examine high time resolution dynamic spectra for fine structures in type II solar radio bursts Methods. We used data obtained with the acousto-optic spectrograph receiver of the Artemis-JLS (ARTEMIS-IV) solar radio spectrograph in the 450–270 MHz range at 10 ms cadence and identified more t...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2019-04, Vol.624, p.A76
Main Authors: Armatas, S., Bouratzis, C., Hillaris, A., Alissandrakis, C. E., Preka-Papadema, P., Moussas, X., Mitsakou, E., Tsitsipis, P., Kontogeorgos, A.
Format: Article
Language:English
Subjects:
Sun: activity
Sun: corona
Sun: radio radiation
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Summary:Aims. We examine high time resolution dynamic spectra for fine structures in type II solar radio bursts Methods. We used data obtained with the acousto-optic spectrograph receiver of the Artemis-JLS (ARTEMIS-IV) solar radio spectrograph in the 450–270 MHz range at 10 ms cadence and identified more than 600 short, narrowband features. Their characteristics, such as instantaneous relative bandwidth and total duration were measured and compared with those of spikes embedded in type IV emissions. Results. Type II associated spikes occur mostly in chains inside or close to the slowly drifting type II emission. These spikes coexist with herringbone and pulsating structures. Their average duration is 96 ms and their average relative bandwidth 1.7%. These properties are not different from those of type IV embedded spikes. It is therefore possible that they are signatures of small-scale reconnection along the type II shock front.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/201834982