Paper detail

Shock Signatures of the Successive Type-II Solar Radio Bursts at Meter Wavelength

The successive type-II solar radio bursts observed on 31 July 2012 by the Bruny Island Radio Spectrometer (BIRS) in the frequency range between 62 - 6 MHz is reported and analyzed. The first type-II radio burst shows clear fundamental and harmonic band structures, while only one band is observed for the second type-II radio burst and is considered as the harmonic band. The first type-II radio burst is observed in the frequency range of 57 - 27 MHz between 00:03 - 00:09 UT at the harmonic band. The second type-II burst is observed between 00:18 - 00:27 UT in the frequency range of 43 - 17 MHz. The type-II radio bursts are associated with a C6 class flare located at the south-eastern limb (S24E87) and a CME observed from STEREO and LASCO observations. The EUVI signatures of the CME is observed in the ST-B EUVI FOV between 23:56 (on 30 July 2012) to 00:06 UT (on 31 July 2012), and are observed in the ST-B COR1 FOV between 00:10 - 00:35 UT moving within an average speed of 725 + or - 101 km/s. The CME is observed in the LASCO C2 FOV after 00:12 UT as a partial halo CME moving with an average speed of 486 km/s. The height-time plot shows that the first type-II radio burst was formed by the CME-shock along the shock front and the second type-II radio burst along the shock-dip structure, probably the dip structure results from the shock transiting across the high dense streamer structure. The successive type-II bursts are most likely produced by the single CME shock and their interactions with the streamer structures. The first type-II radio burst by the CME shock and the second type-II radio burst by the CME shock-streamer interactions.