Theory of Multiply Charged Anomalous Cosmic Rays

The theory of the acceleration, ionization, and transport of anomalous cosmic ray oxygen, including all eight nonzero charge states, is discussed in the framework of a model in which the primary acceleration occurs at the termination shock of the solar wind. This generalizes previous work that considered only singly charged anomalous cosmic rays. The ratio of multiply charged to singly charged anomalous cosmic rays in the inner heliosphere is found in simulations to increase rapidly above a characteristic energy T c of ~20 MeV nucleon -1 . The value of T c is not very sensitive to variations in the parameters, but it does increase somewhat as the particles' characteristic acceleration time is decreased. T c is close to the electrostatic potential between the heliospheric pole and equator, suggesting that singly charged particles cannot be readily accelerated beyond this potential energy whereas those with higher charge can. These simulation results are found to be in good agreement with recent SAMPEX observations, reported in a companion Letter.