2026 Workshop: What are polar cap patches?

Polar cap patches have long been discussed as F-region plasma density enhancements at least twice the background density, typically ~100-1000 km across. However, debate persists on whether this definition is accurate, helpful, or if "patches" encompass multiple phenomena, given that soft precipitation, Traveling Ionospheric Disturbances (TIDs), and Tongues of Ionization (TOIs) can also produce localized plasma density enhancements. Observational biases further complicate classification. It is therefore argued that in modern high-latitude research this definition is more confusing rather than clarifying. This grand challenge seeks to evaluates “patches” from modeling, theory, and observational perspectives, by bringing together experts not only in polar cap structuring, but also waves and other high-latitude phenomena to see evidence of similarities and differences in different identified structuring in the polar cap and come to some consensus about whether or not present categorization makes physical sense, or if it should be reconsidered. These are now achievable with the availability of the long-term observations in the polar cap, and the recent advances in numerical simulations such as MAGE, GITM and GEMINI. This grand challenge will feature talks providing background and an extended discussion period, with a focus on keeping the session structured. We encourage submissions contributing to this debate and especially welcome participation from students and early-career researchers, as evolving definitions will shape future studies of the polar cap.

This year's session will focus on the themes of Patch/Polar TID Generation and Dynamics front the Thermospheric Perspective and Small-Scale Irregularities and Plasma Instability Physics Associated with Patches.