A Novel Technique for Remote Sensing of Mesospheric Temperatures with the NASA EZIE Mission

The Electrojet Zeeman Imaging Explorer (EZIE) mission employs measurements of the Zeeman-split O₂ 118.75 GHz polarized microwave emission to remotely sense magnetic fields associated with ionospheric electrojet currents. In addition to its primary science objectives, EZIE measurements are also sensitive to the mesospheric temperature altitude structure and line-of-sight Doppler shifts, enabling new measurements of the mesosphere and lower thermosphere (MLT).

We describe the technique used to retrieve mesospheric temperature profiles from EZIE brightness temperature spectra. The retrieval exploits the dependence of the O₂ 118.75 GHz spectral line shape on atmospheric temperature and pressure, as well as its polarization properties, using an iterative inversion framework applied to multi-polarization radiance measurements. Temperature information is encoded in the spectral width and shape of the emission, with the highest sensitivity in upper stratosphere and mesosphere.

We present initial EZIE temperature retrievals that reveal coherent mesospheric temperature structures consistent with wave-like variability in the MLT region. We also briefly discuss the sensitivity of the measurements to line-of-sight Doppler shifts associated with neutral winds, noting that vertical wind shear and broad contribution functions complicate direct wind interpretation. These results demonstrate the high potential of EZIE measurements to provide new constraints on mesospheric thermal structure and dynamics, complementing existing observational techniques and contributing to studies of MLT coupling processes.