ON DEFINING INTERPLANETARY CORONAL MASS EJECTIONs FROM FLUID PARAMETERS

Because the majority of spacecraft that observe Interplanetary Coronal Mass Ejections (ICMEs) reside in the neighborhood of the Earth while the best coronagraph observations of Coronal Mass Ejections (CMEs) are of eruptions orthogonal to the Earth–Sun line, the observation of a causative CME on the Sun is not a prerequisite for defining an ICME seen in space. Several observers have compiled lists of ICMEs for the ascending and maximum phase of solar cycle 23 based on varying criteria but derived from a common database: WIND and ACE solar wind and IMF measurements. The criteria include a stronger than ambient magnetic field, rotating magnetic field, low beta, low ion temperature, declining velocity profile, and other characteristics. When we examine the events on these lists we find that these various lists differ considerably. Of the 240 events identified on one or more lists only 22 are consensus identifications. Even when the groups do agree on the identification of an event, they do not agree on when the event starts and stops. Sometimes these differences are of only a few hours but at times they can be up to a day difference. Herein we illustrate the disparity in ICME lists and propose a scheme for rating ICMEs according to the behavior of their fluid parameters in comparison with the flux rope paradigm.