OBSERVATIONS OF THE NEUTRAL ATMOSPHERE BETWEEN 1100 AND 200 KM USING ARIA ROCKET-BORNE AND GROUND-BASED INSTRUMENTS

The atmospheric response in the aurora (ARIA) rocket was launched at 1 406 UT on March 3, 1992, from Poker Flat, Alaska, into a pulsating dif fuse aurora; rocket-borne instruments included an eight-channel photom eter, a far ultraviolet spectrometer, a 130.4-nm atomic oxygen resonan ce lamp, and two particle spectrometers covering the energy range of 1 -400 eV and 10 eV to 20 keV. The photometer channels were isolated usi ng narrow-band interference filters and included measurements of the s trong permitted auroral emissions N-2 (337.1 nm), N: (391.4 nm), and O I (844.6 nm). A ground-based photometer measured the permitted N-2(+) (427.8 nm), the forbidden O I (630.0 nm), and the permitted O 1(844.6 nm) emissions. The ground-based instrument was pointed in the magneti c zenith. Also, the rocket payload was pointed in the magnetic zenith from 100 to 200 km on the upleg. The data were analyzed using the Stri ckland electron transport code, and the rocket and groundbased results were found to be in good agreement regarding the inferred characteris tic energy (E(0) approximate to 3 keV) of the precipitating auroral fl ux and the composition of the neutral atmosphere during the rocket fli ght. In particular, it was found that the O/N-2 density ratio in the n eutral atmosphere diminished during the auroral substorm, which starte d about 2 hours before the ARIA rocket flight. The data showed that th ere was about a 10-min delay between the onset of the substorm and the decrease of the O/N-2 density ratio. At the time of the ARIA flight t his ratio had nearly returned to its presubstorm value. However, the d ata also showed that the O/N-2 density ratio did not recover to its pr esubstorm value until nearly 30 min after the particle and joule heati ng had subsided. Both the photometer and oxygen resonance lamp data sh owed the presence of structure in the atomic oxygen densities in the r egion above 130 km. The observed auroral brightness ratio B-337.1/B-39 1.4 equaled 0.29 and was in agreement with other recent measurements. This ratio was also consistent with the greater than expected flux of secondary electrons measured by the onboard particle spectrometer betw een 40 and 10 eV.