An ionospheric E-region nighttime model

Abstract

A series of five rocket flights was launched from Wallops Island during a 6-hr period on the morning of 22 February 1968. Electron density profiles were measured with a Langmuir probe during ascent and glowing vapor was released for wind measurements during descent. The measured winds were combined with a theoretical E-region model to evaluate scattered solar Lyman-β radiation as a nighttime ion production source using individual ionization profiles. The E-region ionization model included standard ion chemical reactions and laboratory values for rate coefficients. Results showed that the major features of the observed nighttime electron density profiles could be duplicated with molecular ions if wind transport effects and a nighttime ion production source were included. The persistence of two ion layers below 105 km, however, suggested the origin of metallic ions on this particular night. The ionization level for the nighttime profiles was adequately supplied by the assumed Lyman-β brightness (10 Rayleighs). The theoretical dawn profile (0602 EST and 98° zenith angle) required an increase of 3 in the Lyman-β brightness to achieve agreement with the experimental profile. This increase in the scattered radiation was shown to be consistent with measurements and radiation transport calculations.