7.1.4 Wind model of the Earth’s homosphere and heterosphere

The Horizontal Wind Model (HWM) is a comprehensive empirical global model of horizontal winds in the mesosphere and thermosphere (middle and upper atmosphere). The HWM-93 model [RN.6] is based on accumulated measurements made using a variety of observational techniques, including satellite, radar, and ground-based optical remote sensing. The model is used to provide the necessary winds, accounting for time, space and geophysical variations, for many ionospheric, dynamical, and aeronomical calculations It provides meridional (+ northward) and zonal (+ eastward) speed and covers all altitude regions.

Two indices are used in this model:

• F10.7 (both the daily value of the previous day and the 81-day average centred on the input day),

• A_p (daily value).