Interplanetary CMEs Without Observed Coronagraph CMEs

29^th International Cosmic Ray Conference, Pune, India, 2005

Interplanetary CMEs Without Observed Coronagraph CMEs

G.M. Simnett
School of Physics and Astronomy, Univ. of Birmingham, UK

S.W. Kahler
Air Force Research Laboratory, Space Vehicles Directorate, Hanscom AFB, MA, USA

Abstract

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 R_sun 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.