High Latitude Thermospheric Wind Model (HL-TWiM)

We present an empirical model of high-latitude thermospheric winds (HL-TWiM - High Latitude Thermospheric Wind Model) that represent F-region neutral winds as a function of day, latitude, longitude, local time, and geomagnetic activity. HL-TWiM is based on comprehensive statistical analyses of 40 years of long-term thermospheric neutral wind observations from 17 ground-based stations located at various northern and southern high latitudes and 4 space-based instruments. First, we describe how we combine these disparate databases into a coherent picture while overcoming the sampling limitations and biases among them, and then constructing a meaningful statistical response of high-latitude winds as function of day, latitude, longitude, local time, and geomagnetic activity in magnetic coordinates. HL-TWiM is then compared to the neutral wind databases and to NCAR TIEGCM (which encapsulates the present physics-based understanding of high-latitude thermosphere and ionosphere coupling). HL-TWiM set a necessary benchmark for validating new high-latitude observations and first-principles models. In the future, we plan to incorporate the HL-TWiM results into an updated version of the Horizontal Wind Model (HWM14).