Layer-like IR limb emission enhancement observed by SABER/TIMED in the mesosphere and lower thermosphere region

We report first results of our study of characteristics and variability of the layer-like IR limb 4.3 mm daytime emission enhancement observed by SABER/TIMED utilizing nearly a decade of SABER observations. The enhancement is observed in a localized region of the mesosphere and lower thermosphere (MLT) at a tangent height between 85 and 95 km. Also, it has a distinct spatial and temporal variability, and is not predicted by current Non-Local Thermal Equilibrium (NLTE) models for generation of the IR molecular emissions in the MLT. We discuss the characteristics and variability of this layer, compare them with similar effects detected by other instruments, and consider possible physical processes which may influence formation of the IR radiation in the MLT to explain the observed emission enhancement.