The error analysis of the MIGHTI neutral wind velocity retrieval with respect to the non-uniformity of the 630.0 nm airglow

The neutral wind is one of the products from the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) onboard NASA's Ionospheric Connection Explorer (ICON) mission. MIGHTI measures the Doppler shift of the green (557.7 nm) and red (630.0 nm) atomic oxygen emissions from 90 km to 300 km altitude. There are two identical interferometers (MIGHTI-A and MIGHTI-B) that are pointing 90 degrees apart so that the neutral wind vector may be retrieved. While combining MIGHTI-A and MIGHTI-B, one assumes both the average wind vector and the brightness of the airglow, seen by the two interferometers, are the same. Harding et al. (2017) has shown that large errors occur when MIGHTI's line of sight crosses the terminator as well as the edge of the equatorial ionization anomaly by employing a 3D airglow model. These two regions are where large horizontal gradients in both the wind and the emission rate exist. Observations also show non-uniformities in the airglow which are strong gradients in the emission rate. The error coming from non-uniformities is crucial to the interpretation of the dynamics seen by MIGHTI. With a spatial resolution of about 500 km the wind retrievals may be impacted by ionospheric structures of that size (e.g., equatorial plasma bubbles, traveling ionospheric disturbances (TID), and the midnight brightness wave). We use 630.0 nm airglow data from the Imager of Sprite and Upper Atmospheric Lightening (ISUAL) onboard Formosat-2 to study how MIGHTI will see these non-uniformities and how they will affect the data quality.