Super-short structures in solar radio bursts

Jasmina Magdalenic

P. Zlobec, B. Vrsnak, A.Hillaris, M Messerotti

Analysing the high time resolution data (1 ms) recorded by the OAT-multichannel radiopolarimeter we found a new family of very fast radio structures occurring in type IV bursts. The credibility of these super-short structures (SSS-es) is confirmed by one-to-one identification of individual SSS events in the corresponding Artemis-IV spectral recordings. SSS-es appear only in the fine structure rich type IV bursts, sometimes occurring stochastically, and sometimes forming quasi-periodical trains.

SSS-es are generally 2-3 times shorter than the radio spikes, up to now considered to be the shortest features legibly recorded in radio bursts (Güdel & Benz, 1990). The fastest SSS-es are found to be ten times shorter than spikes at the same observing frequency. Typical durations at 237 MHz are found to be around 50 ms (down to 20 ms), then systematically decreasing with the increasing observing frequency, roughly as 1/f. Another distinction in respect to spikes is a stochastic change of the degree (0-100 %) and even the sense of polarization within a given group of SSS-es.A careful analysis of the spectral and single-frequency morphology reveals that, in fact, there are several distinct categories of SSS-es, but all of them being narrow-banded (few MHz).