Observation of energy-dependent ionic charge states in impulsive solar energetic particle events

Authors: Klecker, B., E. Möbius, M. A. Popecki, L. M. Kistler, H. Kucharek and M. Hilchenbach
Reference: Adv. Space Res., 38, 493 - 497, 2006

Abstract: We measured the mean ionic charge state of Fe in several $^3$He-rich and heavy-ion rich energetic particle events during the time period 1998--2000. We combined the ionic charge measurements of CELIAS/STOF onboard SOHO (10--100 keV/nuc) with the measurements of SEPICA onboard ACE (180--550 keV/nuc) to investigate the ionic charge distribution of Fe over a wide energy range. Whereas the mean ionic charge of Fe, $Q_m$(Fe), in the energy range 180--550 keV/nuc increases strongly with energy from $\sim$14--16 by $\sim$2--4 charge units, the mean ionic charge at lower energies of 10--100 keV/nuc was found to be significantly lower (12.5$\pm$0.9). A comparison of the results with steady-state models that include impact ionization by protons and electrons in the low corona shows that the measured increase of $Q_m$(Fe) with energy is often steeper than predicted by the model, and other effects, as for example adiabatic deceleration during the propagation, may play an important role.

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Last Update: November 6, 2007, Corrado Giammanco