Twilight enhancement of 6300 A (OI) airglow
Bennett, Bob, 1984-
O'Brien, B. J.
Master of Science
From consideration of the excitation mechanisms of 6300 A (01) airglow, it is found that an observed twilight enhancement in the- 6300 A (01) intensity may be attributed to a photoelectron flux from the sunlit magnetic conjugate point. This is supported by the coincidence of the beginning of the observed predawn enhancement with the conjugate point sunrise. Airglow intensity measurements were obtained at Houston, in addition to data from international IGY and IQSY observatories. The predawn enhancement is found to have an average value of ~ 50 Rayleighs and a maximum of ~ 100 Rayleighs. Latitudinal limits of the enhancement are determined to be L ~ 1.1 to L ~ 3.2. Over the solar cycle, the enhancement is found to decrease by 50% during periods of minimal solar activity. From the measured intensity enhancements the required photoelectron fluxes are calculated. Between L ~ 1.1 and L ~ 3.2, the average conjugate flux of 10 ev photoelectrons is found to be 2 x 10 to the 8th cm -2 sec -1, which agrees with recent theoretical calculations. The potential significance of this study lies in its implications for magnetospheric electric fields and in the coincidence in L value of the twilight enhancement upper limit and the plasmapause.