Tracking Nonradial Motions and Azimuthal Expansions of Interplanetary CMEs with the Solar Mass Ejection Imager

Abstract

The trajectories of interplanetary CMEs (ICMEs) are modified by their interactions with solar wind streams. These interactions can result in non-radial deflections of ICME trajectories and changes to their rates of azimuthal expansion. The Solar Mass Ejection Imager (SMEI), launched earlier in 2003 January, has provided heliospheric images of several hundred ICMEs during the declining portion of solar cycle 23. We selected three SMEI ICMEs, each traversing a range of solar elongation angles ɛ>20°, and measured the time changes of their leading-edge profiles plotted against position angle, PA. The parabolic fits to those profiles yielded the propagation directions of the ICMEs as well as their leading-edge curvatures and time profiles. The selected ICMEs were associated with LASCO CMEs, so we tracked the PA variations in their propagation over 1 to 3-day periods. We found good fits for two of the ICMEs, but one yielded generally poor fits.