2025 Workshop: Ionospheric Scintillation and Plasma Density Irregularities

Given the well-attended sessions last time, insufficient time to address the proposed topics and community interest in the topic, we are resubmitting a continuation of our previous proposal with slight modifications.

Phase and amplitude scintillation of GNSS radio waves traveling from satellites to receivers through ionospheric plasma leads to reduced ability to obtain accurate position, navigation and timing (PNT), which impacts a variety of societally important operational systems. It is clear that plasma density enhancements during geomagnetically active times contribute to this problem, modifying both refractive and diffractive effects. These plasma density structures undergo spatio-temporal evolution as the scintillation is occurring. Many questions remain unanswered about the distinct effects on GNSS scintillation induced by a wide variety discrete auroral structures. Phase and amplitude scintillation both occur in these regions, but their similarities and differences in altitude, magnetic latitude and magnetic longitude are still widely debated. In addition, with regard to diffractive scintillation, it is unclear what plasma instability magnifies the density irregularities to cause appreciable effects. Finally, several indices (ROTI, sigma_phi, S_4, IFLC, etc.) are often applied to characterize scintillation effects, and the indices do not always agree, and also vary in relation to optical Fresnel radius and frequency. In short, ionospheric scintillation is a unified topic of study with many questions in need of resolution through focused community-wide collaborative efforts. Its practical impacts on space weather and operations demand a deeper understanding of the underlying physical phenomena.

A wide variety of observational and instrumentation strategies apply to this topic as well, including scatter radars, GPS satellites and receivers, ground magnetometers and all-sky imagery. Data assimilation techniques and total electron content maps, both data-based and model based, are often used in order to study local and global plasma density structuring in response to solar wind driving of the magnetosphere-ionosphere system. These approaches, when integrated, will allow further clarification of the general geospace system and its dynamical evolution.