Observation of suprathermal helium at 1 AU: Charge states in CIRs Available to Purchase

We report on measurements of the He charge states as observed in recurring energetic particle events during the recent solar minimum in 1996. The time-of-flight mass spectrometer CELIAS/STOF on board the SOHO satellite has the capability of detecting energetic ions between 35 and 630 keV/q and determine the mass, energy and charge of each particle. Typically we observe a $He+/He2+$ ratio of 0.16 to 0.31 in the range of 25 to 150 keV/nuc. We discuss the implications of these observations on the existing models of particle acceleration in corotating interaction regions (CIRs), i.e. the location of the acceleration process of corotating particle events as observed near 1 AU.