Paper presented at the EGS General Assembly, 21-25, April, 1997, Vienna, Austria
The time-of-flight mass spectrometer STOF (and HSTOF) of the CELIAS sensor on SOHO has the capability of detecting energetic ions between 35 and 700 keV/q (or up to 1 MeV/nuc in HSTOF) and determines the mass, energy and charge (charge upper limit in HSTOF) of each particle. We shall report on the flux ratio of He+ and He2+ derived from the data collected since launch and discuss the implications of this observation on the existing models of particle acceleration in co-rotating interaction regions (CIRs), i.e. the seed particle population for the acceleration process of corotating particle events.