Interplanetary and Geomagnetic Consequences of Interacting CMEs of 13 – 14 June 2012

We report on the kinematics of two interacting CMEs observed on 13 and 14 June 2012. The two CMEs originated from the same active region NOAA 11504. After their launches which were separated by several hours, they were observed to interact at a distance of \(100~R_{\odot}\) from the Sun. The interaction led to a moderate geomagnetic storm at the Earth with minimum \(\mathrm{D}_{\mathrm{st}}\) index of approximately −86 nT. The kinematics of the two CMEs is estimated using data from the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument onboard the Solar Terrestrial Relations Observatory (STEREO). Assuming a head-on collision scenario, we find that the collision is inelastic in nature. Further, the signatures of their interaction are examined using the in situ observations obtained by Wind and the Advance Composition Explorer (ACE) spacecraft. It is also found that this interaction event led to the strongest sudden storm commencement (SSC) (\({\approx\,}150\) nT) of the present Solar Cycle 24. The SSC was of long duration, approximately 20 hours. The role of interacting CMEs in enhancing the geoeffectiveness is examined.