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How do atmospheric tides and gravity waves affect the E region?
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Ionosphere and magnetosphere
The layers of Earth's atmosphere, with a yellow line showing the air temperature at various heights.
Atmospheric tides and gravity waves significantly influence the E region of the ionosphere by driving the movement of ionization and shaping its structure.1
- Concentrating Ionization: Both tides and gravity waves are responsible for concentrating ionization into layers. As these waves propagate upward into regions of lower density, their amplitude increases significantly, creating strong alternating horizontal winds. These winds can drive ionization up or down along inclined magnetic field lines. When winds at different altitudes blow in opposite directions, they cause a "bunching" of ionization, leading to local enhancements in electron density known as sporadic E.1
- Driving Currents: In conjunction with large-scale wind systems in the lower thermosphere, these waves help drive irregular electrical currents. This process, occurring in the dynamo region, is associated with an electric field that modulates the magnetic field, most notably forming the electrojet at the equator.1
While atmospheric tides result from the regular diurnal cycle of heating and cooling, gravity waves arise from irregular forcing, such as thunderstorms or airflow over mountain ranges.1