Implications of Time Variations for the Origin of Low Energy Cosmic Ray Nitrogen and Oxygen Nuclei

Abstract

We report observations of time variations in the quiet time intensity of 5-27 MeV/nuc nitrogen and oxygen and 13-25 MeV/nuc helium nuclei, obtained with the Caltech Electron/Isotope Spectrometers on IMP 7 and 8. We find no significant correlation of the O variations with variations in the low intensity fluxes of 1-2 MeV solar protons. However, we do find the O intensity to be well correlated with the modulation of galactic cosmic rays as measured by neutron monitors. When compared with the neutron monitor, the factor of ~ 3 change in the 0 intensity during 1972 through 1974 is consistent with the factor of ~ 30 increase observed since 1969. These observations imply that the enhanced low energy N and O fluxes are not of solar origin, but originate far enough from the sun that they undergo substantial modulation and have significantly increased access to 1 AU at times of minimum solar modulation. It may be possible to determine the charge state of the He and O by comparing their time variations. The He and O variations are strongly correlated, and both exhibit similar hysteresis effects when compared to the neutron monitor.