Charge States and Abundances of Heavy Ions as Signatures of Interplanetary Coronal Mass Ejections

Compositional signatures are by now a well-established tool for the identification of Interplanetary Coronal Mass Ejections. An alpha-to-proton ratio of >8 % is a sufficient criterion for the presence of an ICME, as is an average charge state of iron ions of < Q_Fe > ≥ 12; both of these signatures are not necessary ones, though. An increased C and O freezing-in temperature is also likely to be a robust ICME signature. Compositional signatures are particulary attractive because, unlike kinetic and magnetic ones, they remain essentially unchanged throughout the entire heliosphere. Using data obtained with Ulysses-SWICS we evaluate the occurrence rate of composition signatures in ICMEs as identified both by their classical (kinetic and magnetic) as well as by their compositional signatures. We then attempt to identify and define different classes of ICMEs based on the presence of particular, characteristic combinations of such signatures. Finally, the distribution of ICMEs with and without a compositional signature as a function of heliographic latitude will be evaluated.