Abstract
Using instruments onboard the ACE and Wind spacecrafts, we study temporal evolution, spectra, and ionization states of Fe in the impulsive solar energetic particle (SEP) events of September 6, 1998 and May 1, 2000. Proton and electron intensities and anisotropies were used to constrain the particle mean free path in interplanetary space. The derived values were used to explain the observed energy and charge spectra of heavy ions. It is concluded that the sharp increase in the average charge of Fe ions in the range from 200 to 600 keV per nucleon observed in both events cannot be explained within the framework of the model of single-temperature source even if the effects of interplanetary propagation are taken into account. At least two acceleration regions with temperatures ∼106 and 107 K should exist in the source.
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