High resolution observations with Artemis-IV and the NRH I. Type IV associated narrow-band bursts

• Published in: Astronomy and astrophysics (Berlin) Vol. 586; p. A29
• Main Authors: Bouratzis, C, A Hillaris, A, Alissandrakis, C E, Preka-Papadema, P, Moussas, X, Caroubalos, C, Tsitsipis, P, Kontogeorgos, A
• Format: Journal Article
• Language: English
• Published: 01.02.2016
• Subjects: Bandwidth; Bursts; Fine structure; High resolution; Small scale; Spectra; Spectrographs; Spikes
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201527229

Narrow-band bursts appear on dynamic spectra from microwave to decametric frequencies as fine structures with very small duration and bandwidth. They are believed to be manifestations of small scale energy release through magnetic reconnection. We analyzed 27 metric type IV events with embedded narrow-band bursts, which were observed by the ARTEMIS-IV radio spectrograph from 30 June 1999 to 1 August 2010. We examined the morphological characteristics of isolated narrow-band structures (mostly spikes) and groups or chains of structures. The events were recorded with the SAO high resolution receiver of ARTEMIS-IV in the 270-450 MHz range. We measured the duration, spectral width, and frequency drift of ~12000 individual narrow-band bursts, groups, and chains. Spike sources were imaged with the Nancay radioheliograph (NRH) for the event of 21 April 2003. The duration and bandwidth distributions did not show any clear separation in groups. The NRH data indicate that the spikes are not fluctuations of the background, but represent additional emission such as what would be expected from small-scale reconnection.