A.T. Bogdanov1, B. Klecker1, E. Moebius2, M. Hilchenbach3, L.M. Kistler2, M.A. Popecki2, D. Hovestadt1 1 Max-Planck-Institut fuer extraterrestrische Physik, Garching, D-85740, Germany 2 Space Science Center, University of New Hampshire, Durham, NH, 03824, USA 3 Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau, D-37189, Germany
We investigate the energy dependence of the charge states of heavy ions during a number of gradual solar energetic particle events related to coronal mass ejections. The data of two instruments with complementary energy ranges, the Solar Energetic Particle Ionic Charge Analyzer SEPICA on ACE and the time-of-flight mass and charge spectrometer STOF on SOHO are used to cover the energy range from ~ 0.02 to 0.7 MeV/amu for O and Fe. Measurements with SAMPEX and SEPICA/ACE have delivered evidence that some gradual CME related SEP events show energy dependent charge distributions. In the present paper we are closing the gap in the lower energy interval (STOF data) thus making future comparison to solar wind values - representative for coronal conditions - more reliable. The results from such a comparison could contribute decisively to assessing the applicability of available stationary and non-stationary models of the formation of the charge distributions. Also, fitting the data to results of model calculations could be used as a source of information on the temperature and density of the coronal plasma in the acceleration region, as well as a test for the current theoretical understanding of the selection and acceleration mechanisms in CME related solar energetic particle events.