Aims. We examine high time resolution dynamic spectra for fine structures in type II solar radio bursts Methods. We used data obtained with the (SAO) 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.
On 17 January 2005 two fast coronal mass ejections were recorded in close succession during two distinct episodes of a 3B/X3.8 flare. Both were accompanied by metre-494 A. Hillaris et al.to-kilometre type-III groups tracing energetic electrons that escape into the interplanetary space and by decametre-to-hectometre type-II bursts attributed to CME-driven shock waves. A peculiar type-III burst group was observed below 600 kHz 1.5 hours after the second type-III group. It occurred without any simultaneous activity at higher frequencies, around the time when the two CMEs were expected to interact. We associate this emission with the interaction of the CMEs at heliocentric distances of about 25 R . Near-relativistic electrons observed by the EPAM experiment onboard ACE near 1 AU revealed successive particle releases that can be associated with the two flare/CME events and the low-frequency type-III burst at the time of CME interaction. We compare the pros and cons of shock acceleration and acceleration in the course of magnetic reconnection for the escaping electron beams revealed by the type-III bursts and for the electrons measured in situ.
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