The possible effect of solar soft X rays on thermospheric nitric oxide

A rocket measurement of thermospheric nitric oxide (NO) is used to evaluate the production of odd nitrogen by solar soft X rays (18–50 Å). The rocket observation was performed over White Sands Missile Range on November 9, 1981, at 1500 LT for solar maximum conditions ( F 10.7 = 233). The peak observed NO density was 6.3×10 7 cm −3 at 102 km. A photochemical model which included soft X rays was used for comparison with the data. The soft X rays create photoelectrons which lead to enhanced ionization of N 2 and thus increased odd nitrogen production. A good fit to the data was achieved using a soft X ray flux of 0.75 erg cm −2 s −1 .