Synthetic thermosphere winds based on CHAMP neutral and plasma density measurements. Issue 4 (25th April 2016)

• Record Type: Journal Article
• Authors: Gasperini, F.; Forbes, J. M.; Doornbos, E. N.; Bruinsma, S. L.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 4(2016:Apr.)
• Page Start: 3699
• Page End: 3721
• Publication Date: 2016-04-25
• Subjects: CHAMP synthetic wind -- thermosphere wind -- thermosphere tides -- thermosphere wave coupling; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022392
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Meridional winds in the thermosphere are key to understanding latitudinal coupling and thermosphere‐ionosphere coupling, and yet global measurements of this wind component are scarce. In this work, neutral and electron densities measured by the Challenging Minisatellite Payload (CHAMP) satellite at solar low and geomagnetically quiet conditions are converted to pressure gradient and ion drag forces, which are then used to solve the horizontal momentum equation to estimate low latitude to midlatitude zonal and meridional "synthetic" winds. We validate the method by showing that neutral and electron densities output from National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Mesosphere Electrodynamics‐General Circulation Model (TIME‐GCM) can be used to derive solutions to the momentum equations that replicate reasonably well (over 85% of the variance) the winds self‐consistently calculated within the TIME‐GCM. CHAMP cross‐track winds are found to share over 65% of the variance with the synthetic zonal winds, providing further reassurance that this wind product should provide credible results. Comparisons with the Horizontal Wind Model 14 (HWM14) show that the empirical model largely underestimates wind speeds and does not reproduce much of the observed variability. Additionally, in this work we reveal the longitude, latitude, local time, and seasonal variability in the winds; show evidence of ionosphere‐thermosphere (IT) coupling, with enhanced postsunset eastward winds due to depleted ion drag; demonstrate superrotation speeds of ∼27 m/s at the equator; discuss vertical wave coupling due the diurnal eastward propagating tide with zonal wave number 3 and the semidiurnal eastward propagating tide with zonal wave number 2. Key Points: CHAMP neutral and electron densities are used to solve the momentum equations for the zonal and meridional winds HWM14 is found to largely underestimate the latitude, longitude, and local time variability in the winds The zonal and meridional wind longitude structures show large variability with local time and season