Thermospheric neutral winds obtained from data assimilation techniques

Thermospheric neutral winds play an important role in the dynamics of the upper atmosphere. However, direct observations of these winds are limited both temporally and spatially. Radio occultation measurements that probe the ionized part of the atmosphere are abundant and provide critical parameters associated with ionospheric dynamics that embed information about the underlying thermosphere. Data assimilation combines information from observations with a physical model. Observed data are assimilated into the model as a constraint for the physical equations, which in turn allows for an estimation of unobserved driving forces, e.g., the thermospheric neutral wind. The Global Assimilation of Ionospheric Measurements Full Physics model can assimilate global maps of ionospheric parameters obtained from radio occultation measurements to estimate magnetic meridional winds. The Thermospheric Wind Assimilation Model (TWAM) combines these magnetic meridional wind estimates with the equation of motion of the neutral gas using a Kalman filter to provide estimates of the thermospheric wind components. We will present the month-to-month progression of the TWAM thermospheric wind estimates for the year 2009.