Ionic charge states of solar energetic particles from solar flare events during the current rise of solar activity as observed with ACE SEPICA Original Research Article

Ionic charge states of solar energetic ions provide key information on the local temperatures and ionization processes in solar flares. In conjunction with the particle mass this measurement is a tool to study acceleration, fractionation, and transport processes. SEPICA has been designed to resolve charge state distributions in detail and to provide a large collecting power, which allows a much more detailed analysis. During November 4 – 7, 1997, a series of strong flares occurred that were magnetically well-connected. Over the energy range ≈ 0.2 – 1 MeV/nucleon a substantial increase of the charge states with energy was observed. Fe shows a charge state distribution with a distinct peak at Q ≈ 10 – 15 and a tail extending to Q ≈ 20. The newly revealed variation of the charge states with energy will potentially provide insight into modification of charge states during or after acceleration due to stripping and/or rigidity dependent acceleration processes. In addition, a sample of solar particle (SEP) events in 1998, the first year of significant solar activity during the rise of the current solar cycle, is studied for their charge state variations. Typical gradual events that resemble closely coronal composition are found with Fe charge state of ≈11 and impulsive events with high Fe abundance and charge states between 17 and 20. In addition, there are also SEP events with charge states between 12 and 15 that show a moderate, but varying enhancement in Fe. It appears that charge states of SEPs show a much richer variation than the previously reported two groups of charge states, which is also correlated with heavy ion enrichment.