An Intense Flare–CME Event in 2015: Propagation and Interaction Effects Between the Sun and Earth’s Orbit

We report the interplanetary effects of a fast coronal mass ejection (CME) associated with the intense X2.7 flare that occurred on 05 May 2015. The near-Sun signatures of the CME at low-coronal heights [\({<}\,2~\mathrm{R}_{\odot}\)] are obtained from the EUV images at 171 A and metric radio observations. The intensity and duration of the CME-driven radio bursts in the near-Sun and interplanetary medium indicate this CME event to be an energetic one. The interplanetary-scintillation data, along with the low-frequency radio spectrum, played a crucial role in understanding the radial evolution of the speed and expansion of the CME in the inner heliosphere as well as its interaction with a preceding slow CME. The estimation of the speed of the CME at several points along the Sun to 1 AU trajectory shows that: i) the CME went through a rapid acceleration as well as expansion up to a height of \({\approx}\,6~\mathrm{R}_{\odot}\), and ii) the CME continued to propagate at speed \({\geq}\,800~\mbox{km}\,\mbox{s}^{-1}\) between the Sun and 1 AU. These results show that the CME likely overcame the drag exerted by the ambient/background solar wind with the support of its internal magnetic energy. When the CME interacted with a slow, preceding CME, the turbulence level associated with the CME-driven disturbance increased significantly.