Cosmic Ray Spectra and the Solar Magnetic Polarity: Preliminary Results from 1994–2002

Abstract

Each year, beginning in 1994, a U.S./Australia collaboration has conducted a neutron monitor latitude survey from the United States to McMurdo, Antarctica and back over a ∼6‐month period. This experiment permits us to observe the high‐energy cosmic ray spectrum as it evolves from the last solar activity minimum, through the recent maximum and magnetic polarity reversal, and into the early stages of the new polarity epoch. In this work, we focus on the controversial issue of whether a high‐energy (∼8 GeV) “cross‐over” exists in spectra observed during opposite magnetic polarities. We report on a preliminary analysis of the data and discuss our findings. In particular, we investigate the sensitivity of the modulated cosmic ray spectrum to the sign of the Sun’s magnetic field.