Observations and modeling of scintillation in the vicinity of a polar cap patch

Abstract

Small-scale ionospheric plasma structures can cause scintillation in radio signals passing through the ionosphere. The relationship between the scintillated signal and how plasma structuring develops is complex. We model the development of small-scale plasma structuring in and around an idealized polar cap patch observed by the Resolute Bay Incoherent Scatter Radars (RISR) with the Geospace Environment Model for Ion-Neutral Interactions (GEMINI). Then, we simulate a signal passing through the resulting small-scale structuring with the Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere (SIGMA) to predict the scintillation characteristics that will be observed by a ground receiver at different stages of instability development. Finally, we compare the predicted signal characteristics with actual observations of scintillation from ground receivers in the vicinity of Resolute Bay. We interpret the results in terms of the nature of the small-scale plasma structuring in the ionosphere and how it impacts signals of different frequencies, and attempt to infer information about the ionospheric plasma irregularity spectrum.

Phase and Amplitude Scintillations Associated With Polar Cap Patches: Statistical and Event Analyses

“…For example, in the Lamarche et al. (2022) study, they found that there were scintillations found for the UHF and VHF signals, but not for the GNSS L1 signal for a patch event on 21 November 2017 observed by RISR‐C and RISR‐N. They found similar results for this patch using a model, GEMINI.…”

Novel Measurement Architectures Addressing Unresolved Issues Concerning Radio Wave Scintillation and Ionospheric Irregularities

“…In addition to particle precipitation, small-scale structures associated with scintillation can also be generated by a variety of fluid instability mechanisms driven by collisional or inertial processes that are active at high latitudes (Fejer & Kelley, 1980;Tsunoda, 1988). The most commonly invoked instability mechanisms are the gradient drift instability (GDI) (Tsunoda, 1988;Deshpande and Zettergren, 2019;Lamarche et al, 2022), which acts in regions with flow in the direction of a plasma density gradient, and the Kelvin-Helmholtz instability (KHI) (Linson & Workman, 1970;Keskinen & Ossakow, 1981;Keskinen et al, 1988;Spicher et al, 2020), which results from shears combined with ion inertial effects (polarization drift/current). The high-latitude region is populated with strong plasma flows and large-and meso-scale structures comprising varied background gradients and shears.…”

“…Despite the importance of scintillation caused by the ionosphere, critical questions remain concerning where and when scintillation occurs in relation to larger-scale ionospheric phenomena, like equatorial plasma bubbles, aurora, the cusp, and polar cap patches as well as causative physical processes. Past studies have characterized some of the very basic features of scintillation; additionally, a large number of studies have covered various aspects of measurements and theories of ionospheric irregularities and radio wave scintillation caused by turbulent media or different types of irregularities (Deshpande & Zettergren 2019;Spicher et al, 2020;Lamarche et al, 2022) However, we still do not understand the primary generation mechanisms of plasma density irregularities that cause scintillation (Nishimura et al 2021, Deshpande et al 2022, andreferences therein).…”

The Distribution of Small‐Scale Irregularities in the E‐Region, and Its Tendency to Match the Spectrum of Field‐Aligned Current Structures in the F‐Region

“…Frequently evoked, the gradient drift instability depends on density gradients parallel to an ambient electric field, leading to charge separation and the development of polarization electric fields that lead to an E × B ‐drift that amplifies the initial density gradients (Tsunoda, 1988). Gradient drift instability growth rates favor plasma structuring on the order of ∼1 km (Tsunoda, 1988), though that scale‐size is dependent on local plasma physical conditions (Lamarche et al., 2022). In addition, similar disturbances in the auroral region can be caused by flow shear (Horton et al., 1987; Keskinen et al., 1988) and in some cases the current‐convective instability (Kintner & Seyler, 1985).…”