HR: 13:55h
AN: SH33B-02    [Abstracts]
TI: Composition of Interplanetary Coronal Mass Ejections at Very High Latitudes
AU: * von Steiger, R
EM: vsteiger@issi.unibe.ch
AF: International Space Science Institute, Hallerstrasse 6, Bern, CH-3012 Switzerland
AU: Zurbuchen, T H
EM: thomasz@umich.edu
AF: University of Michigan, Department of AOSS, 2455 Hayward St., Ann Arbor, MI 48109 United States
AU: Kilchenmann, A
EM: kilchenmann@issi.unibe.ch
AF: International Space Science Institute, Hallerstrasse 6, Bern, CH-3012 Switzerland
AB: Composition signatures such as a high average iron charge state, a high O$^{7+}/$O$^{6+}$ ratio, or a high alpha to proton ratio are established tools for the identification of interplanetary coronal mass ejections (ICMEs). However, their relation to the classical signatures such as conterstreaming electrons, low plasma beta, or magnetic field rotation, is far from being one-to-one, and therefore deserves some attention. When Ulysses was traveling to high latitudes it encountered ICMEs both during the first set of polar passes at solar minimum and during the second set, which occurred around the maximum of solar cycle 23. Six high-latitude ICMEs had been observed in the large fast streams from the polar coronal holes at solar minimum, defining a new class of overexpanding ICMEs, but none had a compositional signature whatsoever. In this paper we analyze five ICME events that were also embedded in a polar fast stream, but occurred not far from solar maximum, in October to December 2001 at a heliolatitude of $>70^\circ$ north. These five events show a surprising variety of compositional signatures, from hardly any to strong. They are ideally suited for the study of these signatures since the background fast solar wind is compositionally uniform, making the boundaries appear very sharp. This enables us to compare the two sets of signatures to a high degree of accuracy.
UR: http://www.issi.unibe.ch/$\sim$vsteiger/agu\_f04.html
DE: 7511 Coronal holes
DE: 7513 Coronal mass ejections
DE: 2111 Ejecta, driver gases, and magnetic clouds
DE: 2162 Solar cycle variations (7536)
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting