000005355 001__ 5355
000005355 005__ 20210528002624.0
000005355 0247_ $$2DOI$$a10.3847/1538-4357/ab7005 
000005355 037__ $$aSCART-2021-0096
000005355 100__ $$aZhang, P.J.
000005355 245__ $$aThe Frequency Drift and Fine Structures of Solar S-bursts in the High Frequency Band of LOFAR
000005355 260__ $$c2020
000005355 520__ $$aSolar S-bursts are short duration (<1 s at decameter wavelengths) radio bursts that have been observed during periods of moderate solar activity, where S stands for short. The frequency drift of S-bursts can reflect the coronal density variation and the motion state of the electron beams. In this work, we investigate the frequency drift and the fine structure of the S-bursts with the Low Frequency Array (LOFAR). We find that the average frequency drift rate of the S-bursts within 20-180 MHz could be described by df/dt = -0.0077f1.59, combined with previous results in low frequency. With the high time and frequency resolution of LOFAR, we can resolve the fine structures of the observed solar S-bursts. A fine drift variation pattern was found in the structure of S-bursts (referred to as solar Sb-bursts in this paper) during the type-III storm on 2019 April 13, in the frequency band of 120-240 MHz. The Sb-bursts have a quasiperiodic segmented pattern, and the relative flux intensity tends to be large when the frequency drift rate is relatively large. This kind of structure exists in about 20% of the solar S-burst events within the observed frequency range. We propose that the fine structure is due to the density fluctuations of the background coronal density. We performed a simulation based on this theory that can reproduce the shape and relative flux intensity of the Sb-bursts. This work shows that the fine structure of solar radio bursts can be used to diagnose the coronal plasma.
000005355 536__ $$aBRAIN.be project CCSOM/$$cBRAIN.be project CCSOM/$$fBRAIN.be project CCSOM
000005355 594__ $$aSTCE
000005355 700__ $$aZucca, P.
000005355 700__ $$aWang, C.B. 
000005355 700__ $$aBisi, M. M. 
000005355 700__ $$aDa̧browski, B.
000005355 700__ $$aFallows, R. A.
000005355 700__ $$aKrankowski, A.
000005355 700__ $$aMagdalenic, J.
000005355 700__ $$aMann, G.
000005355 700__ $$aMorosan, D. E. 
000005355 700__ $$aVocks, C.
000005355 773__ $$pThe Astrophysical Journal$$v891$$y2020
000005355 8560_ $$fjasmina.magdalenic@observatoire.be
000005355 905__ $$apublished in
000005355 980__ $$aREFERD