Charge states of energetic solar ions from coronal shock acceleration

The near- Sun acceleration of solar Fe ions at a shock wave driven by a coronal mass ejection is modeled using a new numerical code for charge- consistent ion acceleration and a coronal turbulence model that is consistent with observations of time- intensity profiles of solar energetic particles at 1 AU. The model described in this Letter includes effects of the ionic charge equilibration during both the shock acceleration and the downstream transport. Consecutive processes of the ion acceleration and transport result in a kind of plateau in the energy-charge profiles of Fe ions, formed in the similar to 3 - 30 MeV nucleon(-1) energy range during the postacceleration transport from the solar corona to the interplanetary medium, as reported here for the first time. An alternative scenario suggests concurrent processes of particle acceleration and escape, which results in a steady increase of the mean charge of accelerated ions with the logarithm of their energy. The numerical results discussed here demonstrate a crucial importance of accurate measurements of the energy- charge profiles of iron in the energy range above a few MeV per nucleon.