Magnetohydrodynamic waves in interplanetary coronal mass ejections near 1AU observed by WIND spacecraft

Previous observations of interplanetary coronal mass ejections (ICMEs) show that only from 0.3 to 0.68AU did Alfven wave exist in the ICMEs, and rarely discovered at 1AU in ICMEs. Here we present a preliminary statistical result on the existence of magnetohydrodynamic (MHD) waves in ICMEs near 1AU. Based on all of 27 single ICME events which led to major magnetic storms during 1996-2005, several types of MHD waves in ICMEs are identified with the dispersion relations by SVD method: (1) in about 1/3 ICMEs near 1AU, 8 out of 27 events, some Alfven waves exist continuously ; (2) in 13 cases there are fast waves exist in the sheath of the ICMEs; (3) slow waves exist in all events. These observations may show some new clues to the basic wave property and dynamics of ICME.