Drift Calculations on the Modulation of Anomalous Cosmic Rays During the 1998 Solar Minimum Period

Abstract

We present full-drift solutions of the two-dimensional cosmic ray transport equation in an ongoing study to explain ACR observations made in the outer heliosphere. Calculated spectra are compared to 1998 ACR H, He, 0, N, and Ne observations from Voyager I and 2. It is found that the modulation is dominated by diffusion at the spacecraft positions and that the spectra of all the above species can be reasonably explained using a single set of modulation parameters. These include diffusion mean free paths with a magnitude significantly smaller at the shock than at the spacecraft positions.