Conjugate Photoelectrons at L= 5.6 and the 6300Å Postsunset Enhancement
Planetary and Space Science
A series of simultaneous incoherent-backscatter and 6300 Å tilting-filter photometer observations were made in the winter and early spring of 1972 at Chatanika, Alaska. These observations have been combined for magnetically quiet nights to deduce the presence of excitation by two sources in addition to dissociative recombination. The first appears to be a source that is steady for at least three hours, centered about local midnight, but that varies from night to night, taking on values between 10 and 40 Rayleighs for the nights in question. It is suggested that this source may be a flux of low-energy electrons or protons. The second source is impact excitation by electrons from the magnetic conjugate point. The emission due to this source appears to be small immediately after local sunset, rises to a maximum at about 92° conjugate solar zenith angle (CSZA), and then decreases to zero in the vicinity of 105° CSZA. The deduced intensities for this source at 92° CSZA are in the region of 15–30 Rayleighs for local F-layer critical frequencies of 3−2 MHz, respectively.
Vincent B. Wickwar, Conjugate photoelectrons at L = 5[middle dot]6 and the 6300 A postsunset enhancement, Planetary and Space Science, Volume 22, Issue 9, September 1974, Pages 1297-1307, ISSN 0032-0633, DOI: 10.1016/0032-0633(74)90048-8.