Abstract
So far, little work has been done to study the effect of merged interaction regions (MIRs) on the long-term modulation of cosmic rays in more complex two-dimensional (2D) simulations of the heliosphere. In order to address this shortcoming we present calculations for protons with a 2D time-dependent drift model with an emulated wavy heliospheric neutral sheet (HNS) which include MIRs as large idealized outward propagating regions of enhanced interplanetary magnetic field (IMF) magnitude. We find the recovery rate (tr) from the MIR induced cosmic-ray intensity decrease to be polarity dependent, being slower during an A < 0 IMF polarity cycle than during an A > 0 cycle. This slower (tr) causes successive MIRs to contribute quantitatively more toward long-term modulation during such cycles, stressing the decisive role (tr) plays in the modulation process. We also expect MIRs to dominate the long-term modulation of cosmic rays relative to the wavy HNS at neutron monitor energies, large radial distances (r), and with effective crossfield diffusion (K⊥).
Published Version
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