The Middle‐ and Low‐Latitude Neutral Wind Dynamo

The neutral winds in the thermosphere push the plasma through Earth's magnetic field and generate ionospheric currents. In the steady-state electrodynamics, we consider timescales of minutes and spatial scales of 100s km. The electric field is static and the ionospheric current is divergence free. Electric fields are set up in such a way that the divergence of the current driven by electric fields is balanced by the divergence of the wind-driven current. The wind dynamo refers to the electrodynamic forcing by the neutral winds. In this chapter, we introduce the basic principle of the wind dynamo and give an overview of the general behavior of the ion drift and the ionospheric current. We focus on specific aspects of the wind dynamo, such as variations in the evening, the nighttime, and the daytime tidal and wave signatures. The ionospheric electrodynamics are an important part of the ionosphere-thermosphere system. While progress was made on the observational and modeling side of the ionospheric electrodynamics, we still do not fully understand all observations even on the large temporal and spatial scales.