Characterization of the Thermospheric Mean Winds and Circulation During Solstice Using ICON/MIGHTI Observations

• Published in: Journal of geophysical research. Space physics 2022-11, Vol.127 (11), p.n/a
• Main Authors: Yiğit, Erdal, Dhadly, Manbharat, Medvedev, Alexander S., Harding, Brian J., Englert, Christoph R., Wu, Qian, Immel, Thomas J.
• Format: Article
• Language: English
• Subjects: Altitude; Atmospheric models; Circulation; Circulation patterns; Climatology; General circulation models; Geographical distribution; Gravity waves; horizontal winds; ICON; Interferometers; Ionosphere; Latitude; Lower thermosphere; Mean winds; Meridional wind; Michelson interferometers; Momentum; Momentum balance; Northern Hemisphere; remote sensing; satellite observations; Satellites; Solstices; Spacecraft; Summer; Thermosphere; Upper thermosphere; Variability; Wave models; Wind; wind circulation; Wind observation; Winter; Zonal winds
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2022JA030851

Using the horizontal neutral wind observations from the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument onboard NASA's Ionospheric Connection Explorer (ICON) spacecraft with continuous coverage, we determine the climatology of the mean zonal and meridional winds and the associated mean circulation at low‐to middle latitudes (10°S–40°N) for Northern Hemisphere summer solstice conditions between 90 and 200 km altitudes, specifically on 20 June 2020 solstice as well as for a one‐month period from 8 June–7 July 2020 and for Northern winter season from 16 December 2019–31 January 2020, which spans a 47‐day period, providing full local time coverage. The data are averaged within appropriate altitude, longitude, latitude, solar zenith angle, and local time bins to produce mean wind distributions. The geographical distributions and local time variations of the mean horizontal circulation are evaluated. The instantaneous horizontal winds exhibit a significant degree of spatiotemporal variability often exceeding ±150 m s−1. The daily averaged zonal mean winds demonstrate day‐to‐day variability. Eastward zonal winds and northward (winter‐to‐summer) meridional winds are prevalent in the lower thermosphere, which provides indirect observational evidence of the eastward momentum deposition by small‐scale gravity waves. The mean neutral winds and circulation exhibit smaller scale structures in the lower thermosphere (90–120 km), while they are more homogeneous in the upper thermosphere, indicating the increasingly dissipative nature of the thermosphere. The mean wind and circulation patterns inferred from ICON/MIGHTI measurements can be used to constrain and validate general circulation models, as well as input for numerical wave models. Plain Language Summary Atmospheric horizontal winds (i.e., motion of the neutral air), composed of zonal (east‐west) and meridional (north‐south) components, play an important role for the energy and momentum balance of the atmosphere and ionosphere. Due primarily to a lack of observations, winds in the thermosphere are not well sampled. In this study we use the horizontal winds measured from 90 to 200 km altitude by the Michelson Interferometer for Global High‐resolution Thermospheric Imaging instrument onboard NASA's Ionospheric Connection Explorer spacecraft to generate two‐dimensional maps of zonal and meridional winds, and of the resulting horizontal motion (or circulation) in the thermo