Infrared glow above thunderstorms?

Sustained heating of lower ionospheric electrons by thundercloud fields, as recently suggested by Inan et al. [1996], may lead to the production of enhanced infrared (IR) emissions, in particular 4.3-μm CO₂ emission. The excitation rate for N₂(v) via electron collisions is calculated 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-μm radiative transfer are then computed using a line-by-line non-LTE (non-local thermodynamic equilibrium) radiation model. Limb-viewing radiance profiles at 4.3-μm and typical radiance spectra are estimated for five different TC charge distributions and ambient ionic conductivities. Broadband 4.3-μm enhancements of greater than a factor of two above ambient nighttime levels are predicted for tangent heights (TH) in the range ∼80 to >130 km for the most perturbed case, with larger enhancements in selected narrower spectral regions. The predicted IR enhancements should be observable to an orbiting IR sensor.