29th International Cosmic Ray Conference, Pune, India, 2005
Interplanetary CMEs Without Observed Coronagraph CMEs
School of Physics and Astronomy, Univ. of Birmingham, UK
Air Force Research Laboratory, Space Vehicles Directorate, Hanscom AFB, MA, USA
The SMEI has observed 88 interplanetary coronal mass ejections (ICMEs) in 2003.
This work has established that most of those ICMEs, observed beyond ~30°
elongation angles, are associated with bright CMEs with appropriate speeds
and position angles observed out to 30 Rsun in the SOHO LASCO
coronagraph. However, about one quarter of the ICMEs do not have obvious
candidate CME associations despite good LASCO observational coverage. We
examine the characteristics of those SMEI ICMEs without LASCO CME associations
to determine whether or how they differ from the other ICMEs. In particular
we examine the speed profiles and brightness of those ICMEs. We discuss
possible ways in which the ICMEs can arise as discrete observable structures
in the interplanetary medium without being observed to any significant degree
in coronagraph images.