High Spatial and Temporal Resolution Studies of Thermospheric Vector Wind Fields Derived From a Ground‐Based Network of All‐Sky Fabry‐Perot Interferometers

• Published in: Journal of geophysical research. Space physics Vol. 127; no. 8
• Main Authors: Elliott, J., Conde, M. G.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-08-2022
• Subjects: Algorithms; Fabry‐Perot; Interferometers; inverse‐theory; Line spectra; Local flow; meso‐scale; Momentum; Momentum equation; neutral‐winds; Temporal resolution; thermosphere; waves; Wind; Wind fields
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2022JA030481

Simple scaling analysis of terms in the Navier‐Stokes momentum equation for Earth's atmosphere suggests that winds at heights above 120 km should be smooth and laminar, with little spatial variation over horizontal scale lengths smaller than several hundred kilometers. However, there is increasing evidence that this traditional understanding may fail to account for several important processes, including both waves and small‐scale ion‐neutral momentum coupling. Here, we examine the thermospheric neutral wind field over Alaska in unprecedented detail using observations from an array of four ground‐based all‐sky imaging Fabry‐Perot interferometers, processed using a new geophysical inverse algorithm, to derive high‐resolution maps of all three wind components, with a temporal cadence of 30 seconds. The reconstructed high‐resolution neutral winds showed synoptic‐scale agreement with prior observations and previously validated techniques, with all results exhibiting behavior in agreement with basic physics. However, stacked time‐series plots of vector wind components reveal significantly more spatial and temporal structure than previously reported. In particular, the observed responses included complex wave‐like behavior and highly geographically variable vertical winds. Local flow features were observed at spatial scales as small as 100 km at times, with temporal scales as short as a few tens of minutes. Instances of close spatial and temporal correlations were observed between the wind fields reconstructed from green‐line spectra and ionospheric flows observed independently by SuperDARN.
Key Points
Arrays of all‐sky viewing instruments obtain densely sampled Doppler remote sensing of thermospheric winds
Geophysical inverse techniques are well suited for providing near‐optimal spatially resolved reconstructions of thermospheric winds
Mesoscale structures are directly observed in the thermosphere with length scales as low as 100 km