Relativistic solar protons on Bastille Day 2000

Relativistic protons emitted by the Sun on 2000 July 14 (Bastille Day) caused the count rate of high-latitude neutron monitors to increase by 25-40% relative to the preexisting background of galactic cosmic rays. We use a 9monitor network to show that an initial large anisotropy decreased very rapidly to a small value. We model the event with numerical codes based upon the Boltzmann equation, and conclude that solar particle transport was significantly influenced by a reflecting boundary or magnetic bottleneck from an earlier CME that was located ∼ 0.3 AU beyond Earth at the time of the Bastille Day event. We also model Wind low-energy electrons to determine the parallel mean free path over a rigidity range spanning 4 orders of magnitude.