The thermosphere is the layer of Earth's upper atmosphere which is between about 90 and 600 km. Because the potential differences in the magnetosphere map down to the thermosphere, creating the electric field in the thermosphere, there is plasma drift and a potential difference across the polar cap.
Collision is the dominant form of ion-neutral interaction.
Waves propagate up from below the thermosphere, depositing energy there. These models numerically solve the fundamental equations of momentum, energy, and continuity, assuming the ideal gas law as the equation of state for the thermosphere. These models allow for global coverage, assume vertical levels of pressure, and are time-dependent, showing consequences of external forcing and diurnal changes. Using these inputs, a modeler can investigate thermospheric processes. The model can be compared with data for testing and validation.