Investigation of two coronal mass ejections from circular ribbon source region:Origin, Sun-Earth propagation and Geoeffectiveness

In this article, we compare the properties of two coronal mass ejections(CMEs) that show similar source region characteristics but different evolutionary behaviors in the later phases. We discuss the two events in terms of their near-Sun characteristics, interplanetary evolution and geoeffectiveness. We carefully analyzed the initiation and propagation parameters of these events to establish the precise CMEinterplanetary CME(ICME) connection and their near-Earth consequences. The first event is associated with poor geomagnetic storm disturbance index(Dst ≈-20 n T) while the second event is associated with an intense geomagnetic storm of DST ≈-119 n T. The configuration of the sunspots in the active regions and their evolution are observed by Helioseismic and Magnetic Imager(HMI). For source region imaging, we rely on data obtained from Atmospheric Imaging Assembly(AIA) on board Solar Dynamics Observatory(SDO) and Hα filtergrams from the Solar Tower Telescope at Aryabhatta Research Institute of Observational Sciences(ARIES). For both the CMEs, flux rope eruptions from the source region triggered flares of similar intensities(≈M1). At the solar source region of the eruptions, we observed a circular ribbon flare(CRF) for both cases, suggesting fan-spine magnetic configuration in the active region corona.The multi-channel SDO observations confirm that the eruptive flares and subsequent CMEs were intimately related to the filament eruption. Within the Large Angle and Spectrometric Coronograph(LASCO) field of view(FOV) the two CMEs propagated with linear speeds of 671 and 631 km s, respectively. These CMEs were tracked up to the Earth by Solar Terrestrial Relations Observatory(STEREO) instruments. We find that the source region evolution of CMEs, guided by the large-scale coronal magnetic field configuration,along with near-Sun propagation characteristics, such as CME-CME interactions, played important roles in deciding the evolution of CMEs in the interplanetary medium and subsequently their geoeffectiveness.