A Solar Cycle of Cosmic Ray Fluxes for 2006–2014: Comparison between PAMELA and Neutron Monitors

Abstract

AbstractA comparison of cosmic proton spectra directly measured by the Payload for Antimatter Matter Exploration and Light‐nuclei Astrophysics (PAMELA) experiment during 2006–2014 with data of polar neutron monitors for the same time interval is presented. It is shown that the measured spectra are well described by the force‐field model for the modulation potential range 350–750 MV. The obtained modulation potential agrees with that calculated from the data of the world neutron monitor network for low solar activity between 2006 and 2012 but diverges during the maximum of solar cycle. The empirical relation between the modulation potential and the (inverted) neutron monitor count rate appears somewhat steeper than the modeled one, as confirmed also by data from fragmentary balloon‐borne measurements. A reason for the discrepancy is unclear and calls for additional study using independent data sets.