Recently, oscillations were recognized in the global X–ray flux detected during the 18 April 2014 M7.3 flare by the Fermi/GBM instrument as well as in the spatially localized UV measurements of the IRIS satellite and the EIS/Hinode instruments (Brosius and Daw, 2015, Brosius, Dawn and Inglis, 2016, and Brannon, Longcope, and Qiu, 2015). Radio observations of this flare were also analyzed by Carley, Vilmer, and Gallagher (2016).
The overall radio spectrum consisted of two e–Callisto radiospectrographs, and two Ondrejov radiospectrographs, covering almost the whole 45–5000 MHz frequency interval for the time interval 12:40–13:10 UT (1s sampling).
All these radio full–disk flux curves reveal a quasi–periodic behavior with peaks that are more or less synchronized in general (Figure 1). Nevertheless, their time coincidence with the EIS and IRIS peaks is in some cases good and in others not so good. We think that this is due to the radio spectrum being a whole–disk record consisting of all bursts at any location.
Figure 1. Global overview of the 18 April 2014 solar flare: Fermi/GBM 26 – 50 keV light curve and the radio fluxes at 5000, 1350, 1100, and 600 MHz. The vertical dotted lines designate times of the EIS emission peaks ...