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

TL;DR

This study analyzes two successive type-II solar radio bursts observed in 2012, linking their features to CME shock interactions with streamer structures, and providing detailed spectral and temporal characteristics of these events.

Contribution

It presents a detailed analysis of successive type-II radio bursts and their association with CME shock interactions with streamer structures, highlighting the formation mechanisms.

Findings

First burst shows fundamental and harmonic bands

Second burst observed only as harmonic band

Both bursts linked to CME shock and streamer interactions

Abstract

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.