Studies of auroral hydrogen emissions in west–central Canada. III. Proton and electron auroral ovals

Abstract

A chain of patrol spectrograph stations was operated from 1964 to 1965 to cover the geomagnetic latitude range 55° to 78 °N near geographic longitude 100 °W. Absolute intensities of hydrogen alpha and the OI(λ 5577) lines have been derived from over 7500 spectrograms. From this data, average Hα and λ 5577 zenith intensities, as a function of geomagnetic latitude and time, were derived. Results are also given for these averages for different ranges of Kp index. Plots were made of the λ 5577 intensities from which estimates of the night glow and proton-excited components had been subtracted. It was found that the center of the proton auroral oval lies a few degrees equatorward of that of the electron oval before midnight and crosses somewhat poleward of it after 0100 hours geomagnetic. The average proton and electron precipitation zones overlap considerably. With increasing magnetic disturbance, the proton precipitation zone spreads equatorward and increases considerably in its peak intensity, although its intensity is not very sensitive to Kp at geomagnetic latitudes above 70°. For low Kp, the Hα intensity distribution is rather symmetrical about midnight, but for high Kp the intensities are highest before midnight and the proton auroral oval has its maximum equatorward extent around 2100 hours.