All Physics Faculty Publications

Document Type

Article

Journal/Book Title/Conference

Annals of Geophysics

Volume

27

Issue

1

Publication Date

1972

First Page

187

Last Page

192

Abstract

Incoherent scatter and tilting filter photometer data from Arecibo Observatory were combined to search for a contribution to the 6300 Å predawn enhancement due to impact excitation by photoelectrons from the magnetic conjugate point. Prior to about 105° conjugate solar zenith angle, calculations of the 6300 Å intensities due to dissociative recombination gave good agreement with the observed intensities. Then, with the arrival of conjugate photoelectrons (confirmed by plasma line enhancements), the observed intensities rose above the calculated, the difference increasing until a plateau was achieved at a conjugate solar zenith angle of about 95°. The difference or residual intensity is attributed to direct photoelectron impact excitation. Significant day-to-day variations in the onset angle and intensity have a strong negative correlation with ionospheric electron density.

Comments

Originally published in Annales Geophysicae. Publisher version available through remote link. Paper Presented at I.A.G.A. Aurora and Airglow Symposium, Moscow, August 1971.