INFERENCE OF ATOMIC OXYGEN CONCENTRATION FROM REMOTE-SENSING OF OPTICAL AURORA

A remote sensing method has been developed for the determination of th e [O]/[O-MSIS] ratio in aurora, using ratios of the O I (557.7 nm) and N-2(+) (391.4 nm) emissions, It is shown that the method can be used for the analysis of measurements integrated along the line of sight, p rovided data only above the emission rate peak are used. The method is applied to the case of horizontal viewing from a vertically oriented rocket so that a large volume of space was sampled around the rocket, The method can potentially be applied to satellite limb images, provid ed some independent information about the location of the aurora is av ailable, as it was for the rocket observations, Photometric measuremen ts of the N-2(+) (391.4 nm) and O I (557.7 nm) emissions obtained duri ng the Energy Budget Campaign 1980 on flight E-2 with the instrument E F11 and its reflight in 1981 were used in the analysis presented, Duri ng the first flight the rocket horizontally viewed two distinct aurora e, a nearby diffuse patch, and a more distant pulsating aurora, Result s obtained by the same EF11 instrument on a second flight through an a uroral are in 1981 are also presented, Two types of atomic oxygen vari ability were found in both of the flights. In the first type, [O] is i ncreased above [O-MSIS] by a factor of 1.5 at 180 km, is equal to the MSIS model at 160 km, and is less than MSIS below that; that is, the s cale height of[O] was increased. The experimental I(557.7)/I(391.4) ra tio was constant with altitude, In the second type, the [O] was deplet ed by about a factor of 2 over tile altitude range of 120-180 km, whil e the 1(557.7)/I(391.4) ratio decreased with altitude. The inferred at omic oxygen concentrations of 0.5 to 2 with respect to MSIS suggested different vertical flows on the two cases, Independent evidence is pro vided by atmospheric composition measurements made during the same cam paign.