Transionospheric

Transionospheric is an adjective used to describe phenomena, signals, or processes that occur as electromagnetic waves travel through the ionosphere, the ionized layer of Earth's upper atmosphere spanning roughly 60 to 1000 kilometers in altitude and comprising the D, E, and F regions. In practice, transionospheric propagation refers to signals that pass through the ionosphere, such as satellite radio links from spaceborne transmitters to ground receivers or inter-satellite links that traverse the ionospheric region.

The ionosphere alters transionospheric radio waves by changing their phase and speed, bending their direction and causing delays, dispersion, and, under irregular conditions, amplitude scintillation. The degree of delay is proportional to the electron content along the path, quantified as the total electron content (TEC). The Earth's magnetic field also induces Faraday rotation, affecting signal polarization depending on frequency and path length. In the D region, absorption and damping at lower frequencies can be significant; in higher frequency bands used by GNSS and satellite communications, refraction and delay are the main concerns.

Mitigation and modeling are central to transionospheric applications. Dual-frequency receivers for GPS and other systems can estimate and remove the ionospheric delay, and empirical or climatological ionospheric models (such as IRI or NeQuick) are used to predict TEC and related effects. Transionospheric studies also provide data on ionospheric structure and dynamics and are essential for improving navigation accuracy, satellite communication reliability, and radio astronomy observations that pass through the ionosphere.