EVIDENCE FOR MULTIPLY-CHARGED ANOMALOUS COSMIC-RAYS

New measurements from the SAMPEX spacecraft show that most anomalous c osmic ray (ACR) oxygen nuclei with energies above 20 MeV nucleon(-1) a re multiply ionized, with ionic charge states of Q = 2, Q = 3, and pro bably higher. This new result contrasts with lower energies, at which most ACRs are singly charged. The observed abundance of multiply charg ed ions agrees with estimates of the fraction of singly charged ACRs t hat undergo electron stripping during acceleration if the timescale fo r acceleration to 10 MeV nucleon(-1) is similar to 1 yr. The existence of multiply charged ACRs helps explain their acceleration to high ene rgies, and it has implications for several other studies.