CIRRIS 1A global observations of 15‐µm CO₂ and 5.3‐µm NO limb radiance in the lower thermosphere during moderate to active geomagnetic activity

Abstract

In this paper we present and discuss the cryogenic infrared radiance instrumentation for shuttle (CIRRIS) 15-•m CO2 and 5.3-•m NO data with respect to limb emission variability and within the context of latitudinal, diurnal, and geomagnetic variations during two days of observations onboard shuttle flight STS 39, April 29-30, 1991. About 50 limb emission profiles were examined for the two emissions. Enhancements were observed at high latitudes relative to midlatitudes and low latitudes at 140 km altitude for the 15-•m CO2 emission (factor of 2-5). The high-latitude enhancement in the 5.3-•m NO emission was larger (factor of 11-14). The high-latitude nighttime data were collected in the auroral zone during a class III aurora. Diurnal variations are examined at midlatitudes. A significant enhancement in the 15-•m emission was observed between 0500 and 0700 LT at 140 and 160 km. This effect was modeled by the SHARC atmospheric generator (SAG) which uses the mass spectrometer incoherent scatter (MSIS) model. Species concentrations from the thermosphere-ionospheremesosphere electrodynamics general circulation model (TIME-GCM) and SAG models were input to the SHARC radiance code to simulate the CIRRIS limb emission data.The TIME-GCM predicted the 15-btm CIRRIS radiances generally well for 100 km < z < 120 km but for higher altitudes the data was consistently a factor of 2 higher. For the 5.3-•m simulation the TIME-GCM predicted the data well at low latitudes and midlatitudes, but some significant discrepancies were found at higher latitudes. The altitude of the peak radiance of the 5.3-•m NO emission was found to vary between 110 to 135 km with little systematic global pattern. During high-latitude auroral events the peak of the 5.3-•m emission was consistently observed at higher altitudes than the peak of the 3914• N2 + first negative emission, in agreement with previous observations.

Quasiclassical trajectory study of NO vibrational relaxation by collisions with atomic oxygen

“…While the calculated v=1 to v =0 rate constant using the two lowest (attractive) potential energy surfaces is approximately a factor of 2 below the experimental measurements of Fernando and A surfaces defined in Equation (10), which decreases from 0.095 at 300 K to 0.060 at 2700 K, is to produce a rate constant which is independent of temperature. As temperature increases, more collisions occur on the higher lying repulsive potential energy surfaces which are ineffective in vibrational relaxation.…”

“…The fact this reaction requires translationally hot atoms to proceed may also explain the large variability of NO density with the geophysical parameters. 10 The reaction of N 2 with ground state O( 3 P) atoms, known to be important in combustion where it produces highly vibrationally and rotationally excited NO, The vibration-rotation excitation of NO produced in the thermosphere by reaction (3), which is endothermic by 3.25 eV, would depend upon the excess energy available.…”

Optical/Infrared Signatures for Space-Based Remote Sensing

“…There were scattered sounding rocket measurements (for example [Stair et al, 1975], a few measurements from CIRRIS-1A [Wise et al, 1995], and a number from the SPIRIT-3 sensors on MSX . Although these earlier experiments provided information concerning the emitting species and helped validate models of the non-LTE mechanisms they gave little or no insight into the global nature of the response and the resulting effect on the thermospheric energy budget.…”

Global variation in the 2.7 µm NO overtone limb‐emission from the lower thermosphere

“…latitude, longitude, season, solar cycle, etc., [Wise et al, 1995] is an indication of the sensitivity of its production and loss mechanisms to these parameters. In the terrestrial thermosphere, nitric oxide is mainly produced during the day by solar radiation [Sharma et is endothermic by about 3724 cm 4 (-•0.45 eV ) and is therefore unlikely to yield detectable thermal emission at temperatures prevailing in the lower thermosphere.…”