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Planetary Radio Emissions VIIIProceedings of the 8th International Workshop on Planetary, Solar and Heliospheric Radio Emissions held at Seggauberg near Graz, Austria, October 25–27, 2016
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Planetary Radio Emissions VIII, pp. 381-390, 2018/08/16
Proceedings of the 8th International Workshop on Planetary, Solar and Heliospheric Radio Emissions held at Seggauberg near Graz, Austria, October 25–27, 2016
On April 7, 2011 a CME was observed originating above the AR NOAA 1176, located behind the solar limb. This CME was associated with type IV burst, type II bursts and groups of J-bursts and type III bursts. Groups of J-bursts and type III bursts were observed from 10:50 to 11:20 UT. There was a group of J-bursts from 10:52 to 10:57 UT, originating from accelerated electrons propagating along high magnetic loops connected with the active region NOAA 1176. The group of type III bursts continued from 11:00 to 11:20 UT. There were a lot of spikes and type IIIb bursts with polarizations up to 80% during the group of type III bursts. Type IV burst began at 11:20 UT at 32 MHz and continued for more than 3 hours. Its maximum flux was about 200 s.f.u., and the polarization achieved 40%. There were 3 type II bursts superimposed by type IV burst. Their drift rates were approximately 0, 10 kHz/s, 25 kHz/s, and it appears that they were radio emissions from different regions of the spherical shock produced by the CME. All type II bursts consisted of tadpoles with ”heads” and ”tails”. Their durations were 4 s and 2 s, and their polarizations were about 10% and 40%, correspondingly. The frequency bands of the ”tails” was up to 10 MHz. Their frequency drift rates could be positive and negative ones, and their absolute values changed from 0.4 MHz/s to 4 MHz/s. Previously we found that decameter type IV bursts oscillated with periods of tens of minutes. The type IV burst observed on April 7, 2011 showed oscillations also. Fourier and wavelet analyses showed periods of about 40 minutes for both fluxes and polarizations. Moreover, it turned out that these periods decreased with time with rates of 0.03–0.07. Interpretations of all decameter phenomena are discussed.