SATELLITE REMOTE-SENSING OF THERMOSPHERIC O N-2 AND SOLAR EUV .2. DATA-ANALYSIS/

The companion paper by Strickland et al. (this issue) describes a tech nique for deriving Q(EUV) and O/N-2 from disk observations of OI 135.6 -nm and N-2 LBH dayglow emission. Q(EUV) refers to the integrated sola r EUV energy flux below 45 nm and is derived from knowledge of the 135 .6/LBH ratio or O/N-2 in conjunction with either the 135.6 nm or LBH i ntensity. O/N-2 refers to the ratio of the atomic oxygen (O) column de nsity to the molecular nitrogen (N-2) column density at a given value of the N-2 column density. Strickland et al. show that the least uncer tainty in derived values O/N-2 occurs in the vicinity of an N-2 depth of 10(17) cm(-2). The O/N-2 values presented in this paper are referen ced to this depth. While Q(EUV) is obtained from the intensity of eith er 135.6 nm or LBH, O/N-2 is obtained from the intensity ratio designa ted by 135.6/LBH. The technique has been used to derive O/N-2 and Q(EU V) values from nadir-viewing far ultraviolet dayglow data obtained by the auroral and ionospheric remote sensor instrument on board the Pola r BEAR satellite. Data are considered from single passes on July 15, 1 6, and 21, 1987, spanning a latitude range from 25 degrees to 55 degre es N. The 3-hour ap index was between 20 and 30 for the first two pass es and only about 5 for the third pass. The 135.6-nm and LBH signals w ere obtained from spectra recorded at a resolution of 3.6 nm from whic h a background was subtracted followed by integration over the interva ls from 134.5 to 139.0 nm and 155.0 to 170.0 nm. Uncertainties were as signed to the signals and their ratios that took into account statisti cal uncertainties in the true signal and in the subtracted background signal. Profiles of derived O/N, with uncertainties reflecting the dat a uncertainties are shown along with mass spectrometer/incoherent scat ter (MSIS) O/N-2 profiles over 25 degrees-55 degrees N. More structure is seen in the profiles on July 15 and 16, which are more disturbed d ays than July 21. In all cases, O/N-2 increases from high to low latit udes. MSIS also shows such an increase but is much less structured. Th e results are shown to agree qualitatively with O/N-2 values obtained from a general circulation model. Derived Q(EUV) values are in the ran ge from 1.1 to 1.4 ergs cm(-2) s(-1) and are in good agreement with va lues derived from the Hinteregger spectrum for the F-10.7 values appro priate to the observations. The results illustrate the potential of th e technique for monitoring thermospheric dynamics through latitudinal and temporal variations in O/N-2 which are signatures of ascending and descending motion in the thermosphere.