An unusual coronal mass ejection: First Solar Wind Electron, Proton, AlphaMonitor (SWEPAM) results from the Advanced Composition Explorer

This paper reports the first scientific results from the Solar Wind Electro n Proton Alpha Monitor (SWEPAM) instrument on board the Advanced Compositio n Explorer (ACE) spacecraft. We analyzed a coronal mass ejection (CME) obse rved in the solar wind using data from early February, 1998. This event dis played several of the common signatures of CMEs, such as counterstreaming h alo electrons and depressed ion and electron temperatures, as well as some unusual features. During a portion of the CME traversal, SWEPAM measured a very large helium to proton abundance ratio. Other heavy ions, with a set o f ionization states consistent with normal (1-2 x 10(6) IC) coronal tempera tures, were proportionately enhanced at this time. These observations sugge st a source for at least some of the CME material, where heavy ions are ini tially concentrated relative to hydrogen and then accelerated up into the s olar wind, independent of their mass and first ionization potential.