31 March 1982 Review Of Some Nonlocal-Thermodynamic-Equilibrium High-Altitude 4.3µm Background Effects
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Abstract
Here we briefly review non-LTE mechanisms for high-altitude atmospheric infrared background emissions near 4.3 µm. We concentrate on non-LTE mechanisms for CO2 4.3 µm emission. In the daytime this includes excitation by absorption of sunlight in the 4.3 and 2.7 µm region by CO2, followed by re-emission near 4.3 µm. In the nighttime, transfer of vibrational excitation to CO2 from excited OH via N2 as an intermediate plays a major role. In the auroral case, vibrational excitation of N2 by precipitating electrons is transferred to CO2 and results in intense 4.3 µm aurora with a time constant in the range of 3 to 30 min. In all cases multiple absorption and re-emission of 4.3 µm photons by CO2, and multiple collisional transfer of vibration quanta back and forth between CO2 and N2, plays an important role. Some examples are given of validation of these effects against high sensitivity data obtained in the infrared measurements programs of the Air Force Geophysics Laboratories (AFGL) via rocketborne sensors. Also, some evidence from the AFGL program for a second 4.3 µm auroral mechanism, weaker but faster than the CO2 mechanism, is discussed. Predictions of auroral nadir and earthlimb structure are also given.
© (1982) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. B. Kumer, "Review Of Some Nonlocal-Thermodynamic-Equilibrium High-Altitude 4.3µm Background Effects", Proc. SPIE 0304, Modern Utilization of Infrared Technology VII, (31 March 1982); doi: 10.1117/12.932681; https://doi.org/10.1117/12.932681
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