Journal of geomagnetism and geoelectricity

The temperature dependent vaporization rate for meteoric particles is applied to estimate the production profile of the upper atmospheric sodium. It is shown that the earlier result estimated using a constant temperature that controls the vaporization process for meteoric particles leads to an underestimation of the thickness of the production profile. A typical production profile of sodium calculated by taking account of a mass distribution of the meteoric particles shows the peak height of about 93km and a thickness (10^-1) of about 26km. This thickness is significantly wider than that of a usually observed sodium layer, so that effective removal process of sodium is required for shaping the sodium layer.

View full abstract

Show abstractHide abstract

A thermospheric nitric oxide (NO) profile was obtained at high solar activity by means of the NO γ band airglow measured with a rocket-borne photometer. The peak NO density occurring at the altitudes 105-110km is larger by a factor of about 3 at high solar activity than at minimum solar activity. This result confirms the inference from the ion density data observed in the E region. The one-dimensional numerical model, which includes photochemical and diffusive processes of nitrogen and ionic species and simulates diurnal variations, was used to investigate the solar cycle variation of thermospheric NO due to the changes in solar EUV flux and thermospheric temperature. If allowing for a significant source of atomic nitrogen due to the N₂ predissociation by solar EUV radiation, the model can reproduce the observed NO profiles around the peak altitude at solar minimum and maximum, whereas it gives too large NO densities above the altitude of about 140km at solar maximum.

View full abstract

Download PDF (2054K)

Register with J-STAGE for free!