During the February 25, 1969, solar proton event, particle measurements from the close‐orbiting satellite Esro 2, and particle and magnetic field measurements outside the magnetosphere from the Heos A1 satellite are available. The Esro 2 data for proton energies from E>27 to E>90 Mev show intensity enhancements in the auroral zone region and in the central polar region relative to the rest of the polar cap. At energies of a few million electron volts such enhancements are significantly less marked. By comparison of observations inside and outside the magnetosphere and by suitable trajectory computations inside the magnetosphere, we explain the auroral zone enhancements at energies >27 Mev in terms of a form of impact zone effect allied to a particle anisotropy outside the magnetosphere. We suggest that the enhancements observed over the polar region may be due to the particle anisotropy outside the magnetosphere plus coupling between the central polar cap lines of force and the interplanetary field lines.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.