Observations of Successive CMEs and their Successive Type II Solar Radio Bursts in the Corona

This paper reports the observations of two coronal shocks from two Coronal Mass Ejections (CMEs) for the Successive type II Solar radio bursts observed on 02 May 2021 in the frequency range of 80 - 1 MHz with the time interval of ~ 20 minutes between them. Both the bursts show clear band splitting features in the harmonic band. The estimated heights for the source of the first type II burst lies in the range of 2.06 - 2.93 R0 with the average speeds of 601 + or - 76, 700 + or - 91 and 783 + or - 105 km/s for 2 X, 3.5 X and 5 X Saito electron density models, and the heights for the source of the second type II burst lies in the range of 2.24 - 3.83 R0 with the average speeds of 1063 + or - 113, 1287 + or - 145 and 1478 + or - 172 km/s. The successive CMEs are observed by the twin Solar Terrestrial Relations Observatory STEREO-A between 11:20 - 12:21 UT in the Extreme Ultra Violet Imager (EUVI) and in the Internally Occulting Refractive Coronagraphs (COR1) FOV, the two coronal shocks are generated by the two successive CMEs observed at (11:30) 11:26 UT and (11:55:00) 11:56 UT according to ST-A (EUVI) COR1 observations and most likely released from the same active region. The average speeds of CMEs at COR1 FOV are about 574 = or - 64 km/s and 595 + or - 82 km/s. The simultaneous observations of the EUV structures and the radio bursts, their coinciding height-time further confirms that the successive CMEs are responsible for the successive shocks and their related radio bursts in the corona. The observed band-splitting in the successive type-II radio bursts provides the compression ratios of 1.26 and 1.45 respectively. Therefore, these observations confirms the presence of shock waves in the corona.