Composition and temperature of the neutral tropic lower thermosphere

A diurnal pair of upper atmosphere composition payloads was launched near 9°30′ south latitude aboard Nike-Apache rockets on March 11, 1965. Higher O/O2 ratios were obtained in the daytime than at night, and the values were approximately equal to those obtained at Wallops Island. The data indicated the existence of atomic nitrogen in the order of 1 to 2% of the molecular species, but the extent of possible instrumental and observational errors precludes a firm conclusion in this respect. Argon-nitrogen turbopause levels of 101 and 103 km were deduced from the daytime and nighttime data, respectively. No conclusive dependence on time or location was noted in these results or those of other flights. Contrary to expectations, the indicated daytime exospheric temperature of 600°K was lower than the nighttime (1100°K).