Number 412 (Story #3), January 27, 1999 by Phillip F. Schewe and Ben Stein THE ADVANCED COMPOSITION EXPLORER (ACE) satellite measures isotope and ionization abundances in the solar wind. On two recent occasions (6 Nov 1997 and 2-3 May 1998) explosions on the sun spewed clouds of particles whose isotope profiles departed from the norm. For the Nov 1997 event, for instance, the presence of higher-than-normal ionized states of certain isotopes indicated that regions of hotter-than-normal portions of the solar corona were involved, and this in turn suggested that several particle-acceleration mechanisms were operating in the sun's atmosphere. The May 1998 event featured charge states, such as triply ionized oxygen and nitrogen, not seen before in solar wind. These comparatively modestly ionized atoms are indicative of the relatively cool (100,000 K) gas in solar prominences; this cooler gas must have gotten caught up in the much hotter coronal- mass-ejection material making its way toward ACE. (Series of articles in the 15 January 1999 issue of Geophysical Research Letters.)