INFRARED GLOW ABOVE THUNDERSTORMS

Sustained heating of lower ionospheric electrons by thundercloud field s, as recently suggested by Inan et al. [1996], may lead to the produc tion of enhanced infrared (IR) emissions, in particular 4.3-mu m CO2 e mission. The excitation rate for N-2(v) via electron collisions is cal culated using a new steady-state two-dimensional electrostatic-heating (ESH) model of the upward coupling of the thundercloud (TC) electric fields. The vibrational energy transfer to CO2 and 4.3-mu m radiative transfer are then computed using a line-by-line non-LTE (non-local the rmodynamic equilibrium) radiation model. Limb-viewing radiance profile s at 4.3-mu m and typical radiance spectra are estimated for five diff erent TC charge distributions and ambient ionic conductivities. Broadb and 4.3-mu m enhancements of greater than a factor of two above ambien t nighttime levels are predicted for tangent heights (TH) in the range similar to 80 to >130 km for the most perturbed case, with larger enh ancements in selected narrower spectral regions. The predicted IR enha ncements should be observable to an orbiting IR sensor.