Energetic particle observations during the 2000 July 14 solar event

Data from nine high-latitude neutron monitors are used to deduce the intensity-time and anisotropy-time profiles and pitch-angle distributions of energetic protons near Earth during the major solar event on 2000 July 14 (also known as the Bastille Day event). In addition, particle and magnetic field measurements from Wind, the Advanced Composition Explorer, and the Solar and Heliospheric Observatory (SOHO) are used in the analysis. The observations are fitted with good agreement between two independent numerical models of interplanetary transport. The rapid decrease of anisotropy from a high initial value cannot be explained by a simple model of interplanetary transport. Hence, we invoke a barrier or magnetic bottleneck consistent with an observed magnetic disturbance from an earlier coronal mass ejection that was located similar to0.3 AU beyond Earth's orbit at the time of the Bastille Day event. This work includes the first treatment of focused transport through a magnetic bottleneck. We conclude that the bottleneck reflected a major fraction (approximate to85%) of the relativistic solar protons back toward Earth.