5355 20210528002624.0 10.3847/1538-4357/ab7005 DOI SCART-2021-0096 Zhang, P.J. The Frequency Drift and Fine Structures of Solar S-bursts in the High Frequency Band of LOFAR 2020 Solar 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. BRAIN.be project CCSOM/ BRAIN.be project CCSOM/ BRAIN.be project CCSOM STCE Zucca, P. Wang, C.B. Bisi, M. M. Da̧browski, B. Fallows, R. A. Krankowski, A. Magdalenic, J. Mann, G. Morosan, D. E. Vocks, C. The Astrophysical Journal 891 2020 jasmina.magdalenic@observatoire.be published in REFERD