Geometric and magnetic properties of coronal flux ropes associated with CMEs leading to geomagnetic storms

We have studied three Interplanetary Coronal Mass Ejections (ICMEs) having clear signatures of magnetic cloud (MC) arrival at 1 AU and their associated solar sources during 2011 to 2013. Comparing the axial magnetic field strength (B₀) of the near-Sun coronal flux-ropes with that of the MC at 1 AU, we have found that the average inferred value of B₀ at 1 AU assuming the self-similar expansion of the flux-rope is two times smaller than the value of B₀ obtained from the results of MC fitting. Furthermore, by comparing the initial orientation of the flux-rope near the Sun and its final orientation at 1 AU we have found that the three CMEs exhibited more than 80° rotation during its propagation through the interplanetary medium. Our study suggests that although the near-Sun magnetic properties of coronal flux-ropes can be used to infer the field strength of the associated MC at 1 AU, it is difficult to estimate the final orientation of the MC axis in order to predict the geo-effectiveness of the ICMEs.