Kinematics of interplanetary coronal mass ejections in the inner heliosphere

We report the kinematic properties of 45 interplanetary coronal mass ejections (ICMEs) detected by SOHO/LASCO coronagraph, interplanetary scintillation (IPS), and in-situ observations during 1997 – 2009. Our analyses show that the ICME speeds converge to the speed of background solar wind with increasing distance. We subsequently find that a linear equation is more suited than a quadratic one to describe the relationship between the acceleration and the relative speed of ICMEs moving faster than the solar wind. This result suggests that the hydrodynamic Stokes’ drag force mainly operates on the above ICMEs. Combining the above three different observations serves to detect many ICMEs between the Sun and the Earth, and is a useful means to study their kinematics.