Charge Dependence of Cosmic Ray Solar Modulation

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Magnetic field irregularities carried by the solar wind sweep charged particles out of the solar system and cause the anti-correlation between cosmic ray fluxes and the level of solar activity. Since electrons and nuclei have greatly different charge/mass ratios, the relation of velocity and magnetic rigidity is significantly different for these two particle species. If the heliospheric magnetic field has long range order, the charge sign of cosmic ray particles can affect their propagation. Recent observations show that a major failure of current modulation models simultaneously reproducing electron and nucleon modulation is related to reversals of the solar magnetic field, which occur every eleven years. Charge dependence, then, should change when the solar field reverses, but differently from that observed. The PIs will conduct a research program extending measurements of charge dependence of cosmic ray solar modulation with a series of balloon flights to determine the time dependence of electron and positron fluxes over a broad energy range. This investigation will determine the importance of large scale order of the heliospheric magnetic field in determining trajectories of charged particles in the heliosphere.