HR: 09:00h
AN: SH11A-04    [PDF]
TI: Charge states and abundances of heavy ions as signatures of interplanetary coronal mass ejections
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: Dept. of AOSS, Univ. of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143 United States
AB: Interplanetary Coronal Mass Ejections (ICMEs) are not easy to recognise. Several signatures are used to identify such events: Counterstreaming electrons, magnetic field rotation and fluctuation, low kinetic temperature, etc. However, an individual ICME rarely shows them all, so identification remains a somewhat subjective art form. Composition signatures were long known to provide a useful identifier: An alpha-to-proton ratio of $>$8% is a sufficient criterion for the presence of an ICME. More recently, a high average Fe charge state was established as another sufficient (but not necessary) signature, as is probably the case for an increased C and O freezing-in temperature. Such signatures are particulary attractive because, unlike kinetic and magnetic ones, they remain largely unchanged throughout the entire heliosphere. Using data obtained with Ulysses-SWICS we evaluate the occurrence rate of composition signatures in ICMEs as identified by their classical signatures. The definition of the appropriate threshold values of these signatures will receive particular attention. Finally, the distribution of ICMEs with and without a compositional signature as a function of heliographic latitude will be evaluated.
DE: 2111 Ejecta, driver gases, and magnetic clouds
DE: 2164 Solar wind plasma
DE: 2169 Sources of the solar wind
DE: 7513 Coronal mass ejections
DE: 7536 Solar activity cycle (2162)
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting