Observation of Suprathermal Helium at 1 AU: Charge States and Abundances in CIRs

Authors: M. Hilchenbach, H. Gruenwaldt, H. Kucharek, B. Klecker, F. M. Ipavich, A. B. Galvin, and R. Kallenbach
Reference: Submitted Solar Wind 9 Paper


We report on measurements of the He charge states and relative He/H abundance ratio as observed in recurring energetic particle events during the recent solar minimum in 1996. The time-of-flight mass spectrometers CELIAS/STOF and CELIAS/HSTOF on board of the SOHO satellite have the capability of detecting energetic ions between 35 and 600 keV/q (or up to 0.6 MeV/nuc in HSTOF) and determine the mass, energy and charge (charge upper limit in HSTOF) of each particle. On average we observe a He+/He2+ ratio of 0.15 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 seed particle population for the acceleration process of corotating particle events.

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Last Update: February 18, 1999, James Weygand