Implications of odd oxygen observations by the TIMED/SABER instrument for lower D region ionospheric modeling

• We document the variability in atomic oxygen inferred by the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) instrument on the NASA/TIMED satellite in the lower mesosphere (50-80 km altitude) according to its diurnal, latitudinal, seasonal and solar cycle components. The dominant variation is diurnal and latitudinal. Below 75 km, seasonal and solar cycle effects are less than 5%. Accordingly, we have developed a simple climatology that depends upon local time and latitude and applied it to a model of the D region of the ionosphere. Between 60 and 70 km, atomic oxygen is important in governing the ratio of negative ions to electrons. Using the SABER O climatology along with a previously published climatology of nitric oxide based upon UARS/HALOE data, we compare our model results both to previous calculations and to a profile of electron density [e(-)] acquired by a rocket launched from Kwajalein Atoll. The model results are shown to be consistent with previously published calculations, but the comparison with the data reveals a dramatic discrepancy whereby the calculated [e(-)] is over an order of magnitude less than the observations below 65 km. The most plausible explanation involves changing the partition of negative charge between molecules such as O-2 which rapidly dissociate in sunlight versus heavier, more stable negative ions. Although observations of [e(-)] below 70 km are difficult and infrequent, more research should be invested to evaluate the pervasiveness and the seasonal, latitudinal and diurnal morphology of this model [e(-)] deficit. This may have practical implications as empirical models of the ionosphere predict a secondary maximum in HF radio absorption in the 70 km altitude region.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

Mesosphere

Ionosphere

D region

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)