Spectroscopic Diagnostics of the Formation of Auroral Arcs

Abstract

The theory and mechanisms for spectroscopic observations of auroral arcs are examined. The emission rate ratios of various spectroscopic features are used to determine the average energy of the auroral particles, noting that only proton bombardment of the atmosphere can produce the observed emissions of atomic hydrogen, Balmer alpha, and Balmer beta. The atomic hydrogen particles can cause excitation, stripping, or ionization. Differences in subsequent electron observations due to the relative energy levels of the bombardment are described, and the use of the First Negative bands of molecular N ions and the ground configuration transition in singly atomic O for optical emission studies is outlined. The mean energy of the bombarding electron flux can be obtained and may be equalled under certain conditions by the proton flux. Finally, the characteristics of an ideal spectrometer for exploring auroral emissions are introduced.