Classification and Properties of Supershort Solar Radio Bursts

Characteristics of supershort structures (SSSs) occurring in the metric solar type IV radio bursts are described. The most important property of SSSs is their duration, which, at half-power, ranges from 4 to 60 ms and is thus much shorter than generally expected for the bursts in the metric range. The comparison of the distributions of SSS durations with those of the spikes confirms that these are completely different classes of bursts. Our analysis is focused on the frequency range 200-450 MHz, providing us with the one-to-one identification of individual SSSs in single-frequency records of the INAF-Trieste Astronomical Observatory (Italy) and in the high-resolution spectral data of Artemis IV (Greece). The analysis reveals a number of different bursts that are classified as simple broadband, simple narrowband, and complex SSSs. The diversity of SSSs has a resemblance to the variety of the well-known metric radio bursts characterized by a 1 s timescale.