Evidence for temperature stratification in theEregion

Abstract

The ion temperature of the upper atmosphere at local noon in the region from 100 to 160 km has been measured directly by means of an ion trap. The ion temperature is expected to be the same as that of the neutral particles, since analysis shows that the thermal relaxation time of ions to neutrals is shorter than that of ions to plasma in the above height range. Above 120 km the experimental temperature profile contains what appears to be a wave‐like temperature variation superimposed on an otherwise reasonable thermosphere profile. The peak‐to‐trough amplitude of the temperature variation is 200°K, and the average wavelength is approximately 12 km. The thermosphere temperature profile parallels predicted thermosphere profiles but may be systematically high. At and below 115 km the shape of the profile deviates from predicted profiles. The temperature is high and increases downward; this increase may be caused by aerodynamic heating of the ions before they enter the trap. The amplitude of the wave‐like temperature variation is consistent with that expected from a gravity wave producing a horizontal wind velocity of 150 m/sec. However, the vertical wavelength is smaller than that believed possible for gravity waves in the altitude interval of interest. On the other hand, measured total extreme ultraviolet energy is insufficient to maintain a quasi‐steady‐state temperature profile of the shape observed.

Ion temperature determination in the ionosphere by retarding potential analyzer aboard sounding rocket

“…Ion temperature variations above 150 km had already been seen by some direct measurements, whereas Knudsen and Sharp [1965] shows a wavelike variation of Ti at 110 km to 160 km, where these variations were consistent with the expected gravity wave produced by neutral wind shear.…”

“…When the angle of attack of the rocket axis is Oa and the tilted probe angle is 0s, the angle of attack of TPI-2 is modulated from 0s -Oa to 0s + Oa in one spin period, as is shown in Figure 5 Below 105 km, the ion temperature increases downward and becomes very high. This increase may be caused by aerodynamic heating of the particles by a shock was around the rocket body [Knudsen, 1965]. At the height range between 100 km to 120 km, Ti is a factor of 2 higher than the model Tn.…”

Gravity wave saturation in the middle atmosphere: A review of theory and observations

“…This structure is particularly evident in the data collected at Wallops Island during winter shown in Figure 2. Unstable lapse rates associated with large-amplitude wave motions were also observed in the mesosphere by Groves [1966] and in the lower thermosphere by Knudsen and Sharp [1965] using an ion temperature measurement technique. Additional indications of wave motions and scales were provided by photographic studies of noctilucent clouds (NLC) occurring at the high-latitude summer mesopause [Witt, 1962;Haurwitz and Fogle, 1969].…”

Electron and ion temperatures in the ionosphere

“…Knudsen and Sharp (1965) using an ion trap on a rocket fired near local noon, observed a wave like variation of T between 100 and 160 kin, the amplitude of the variation being 100°K and the wavelength 12 kIn. The mean value of T. was only 100 0 K above the expected Tg.…”