2023 Workshop: Traveling Ionospheric Disturbances

Traveling Ionospheric Disturbances (TIDs) are a ubiquitous feature that are observed as propagating density perturbations in the F-region ionosphere. They have been detected by many different instruments over many decades. Various physical processes are believed to be responsible for the generation of these wave-like features. TIDs can be driven from above by solar and magnetospheric disturbances, or driven from below by lower atmospheric and surface forcing, including but not limited to tropospheric weather events (hurricanes, tornadoes, tropical cyclones, thunderstorms, etc.), earthquakes, tsunamis, volcanic eruptions, explosions, and spacecraft launches. TIDs generated from different types of sources may exhibit similar or very different characteristics in their spatial and temporal scales, periods, propagation speeds and directions. Meanwhile, TIDs generated from the same type of sources may exhibit different characteristics depending on the local atmospheric and ionospheric conditions. Therefore, it remains a challenge to distinguish TIDs from different types of sources in ionospheric observations.

A key obstacle in developing future space weather forecast systems is to predict the physical mechanisms (and their scales) that drive regional ionospheric perturbations, such as TIDs. There have been recent efforts to mitigate the effects of TIDs on HF geolocation, but in order to predict TID occurrence, their generation mechanisms must be understood. The sparse nature of measurements in the ionosphere makes it unlikely that these questions can be answered via observational methods alone. Comprehensive modeling studies combined with new, multi-instrument observations will be required to obtain closure on these science questions.