Modeling the Effect of the Interplanetary Magnetic Field on Cosmic Ray Muon Shadows

Abstract

Cosmic ray (CR) muon shadows were located using muon data from the MINOS Far Detectorin Northern Minnesota. The shadows were located independently across 3 time periods; near solar minimum, solar maximum, and over the entire 13 year span of the data. A muon distribution for each shadow was then sampled to simulate CR motions near the Sun using the Parker Spiral model of the Sun’s IMF and a dipole model of the Earth’s GMF. The resulting particle distributions were then compared to their position with respect to the Sun. An analytical relationship between the primary CR cutoff energy E0 and the associated shadow deflections was observed. The minimum cutoff energy of the primary CR energy spectrum consistent with the Parker Spiral model was determined to be E0 = 22.8 ± 1.2 TeV. This value is 2-3 times higher than the experimentally determined value. Complexities that can be added to the Parker Spiral Model and affect the overall shift of the the Sun’s cosmic ray shadow are discussed to explain discrepancies. Results show that the Parker Spiral model is most consistent with the the solar minimum shadow and least consistent with the solar maximum shadow, as expected.