Estimation of thermospheric zonal and meridional winds using a Kalman filter technique

Knowledge of the thermospheric neutral wind and its horizontal components is critical for an improved understanding of F region dynamics and morphology. However, to date their reliable estimation remains a challenge because of difficulties in both measurement and modeling. We present a new method to estimate the climatology of the zonal and meridional components of thermospheric neutral wind at low and middle latitudes using a Kalman filter technique. First, the climatology of the magnetic meridional wind is obtained by assimilating seasonal maps of F region ionosphere peak parameters ( N m F 2 and h m F 2 ), obtained from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation data, into the Global Assimilation of Ionospheric Measurements Full Physics (GAIM‐FP) model. GAIM‐FP provides the 3‐D electron density throughout the ionosphere, together with the magnetic meridional wind. Next, the global zonal and meridional wind components are estimated using a newly developed Thermospheric Wind Assimilation Model (TWAM). TWAM combines magnetic meridional wind data obtained from GAIM‐FP with a physics‐based 3‐D thermospheric neutral wind model using an implicit Kalman filter technique. Ionospheric drag and ion diffusion velocities, needed for the wind calculation, are also taken from GAIM‐FP. The obtained wind velocities are in close agreement with measurements made by interferometers and with wind values from the Horizontal Wind Model 93 (HWM93) over Millstone Hill, Arecibo, and Arequipa during December and June solstices, and March equinox. In addition, it is shown that compared to HWM93 the winds from TWAM significantly improve the accuracy of the Ionosphere/Plasmasphere Model in reproducing the observed electron density variation over the Weddell Sea Anomaly.