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

Abstract

We associate new data from icebear, a coherent scatter radar located in Saskatchewan, Canada, with scale‐dependent physics in the ionosphere. We subject the large‐scale icebear 3D echo patterns (treated as 2D point clouds) to a data analysis technique hitherto never applied to the ionosphere, a technique that is widely applied in cosmological red‐shift surveys to characterize the spatial clustering of galaxies. The technique results in a novel method to calculate the spatial power spectral density of the greater ionospheric irregularity field. We compare results from this method to in‐situ plasma density and magnetic field observations from the Swarm mission. We show that there is a remarkable similarity between echo clustering spectra in the E‐region and the field‐aligned current structuring spectrum observed in the F‐region: a clear and characteristic preferred scale (5 km) both in the E‐ and F‐region spectra. We discuss the possibility that this represents evidence of an energy injection into the ionospheric irregularity field via energetic particle precipitation, but offer alternative interpretations with wider connotations for the ionosphere‐magnetosphere system. These findings open new and promising avenues of research for the study of the location of ionospheric scatter echoes with 3D information. It constitutes a novel way to consider the pattern of ionospheric irregularities over wide fields of view when there is an abundance of radar echoes, which allows for the analysis of radar data as point clouds.

Measuring Small-scale Plasma Irregularities in the High-latitude E- and F-regions Simultaneously

“…the E-region. This field was shown to correspond remarkably well to the small-scale structuring in the currents produced by the aurora, on all scales between 1.5 km and 25 km [ 20 ].…”

“…The method correlates the positions of individual three-meter Farley-Buneman (FB) waves in the E-region, and produces a spatial power spectrum of their tendency to cluster in space, by application of Monte-Carlo based tools adapted from cosmological galaxy surveys. The resulting clustering spectrum was demonstrated to match the structuring, or filamentation of the aurora above, as measured by satellites orbiting in the topside F-region [ 20 ].…”

“…The results shown in the present study is based on 114 million individual E-region echoes, that are projected on a spherical shell 105 km above Earth's surface. Motivated by how these echoes appear to cluster on that shell [ 42 ], a new method of analysis applies two-point correlation statistics to echo populations, which allows the estimate of an auto-correlation function for the two-dimensional echo density distribution [ 20 ]. The two dimensions in question are those forming a plane perpendicular to Earth's magnetic field lines.…”

“…A recent study based on the coherent scatter radar ICEBEAR 3D developed a method to simultaneously measure plasma at a large continuous scale interval covering scales between 1.5 km and 25 km [ 20 ]. The method correlates the positions of individual three-meter Farley-Buneman (FB) waves in the E-region, and produces a spatial power spectrum of their tendency to cluster in space, by application of Monte-Carlo based tools adapted from cosmological galaxy surveys.…”

Investigating Spatial and Temporal Structuring of E‐Region Coherent Scattering Regions Over Northern Norway

“…A recent study by Ivarsen, Lozinsky, et al. (2023) has also shown the decrease in magnitude of slopes at ∼ 10 km scales, where the decrease is clearly interpreted as an increase in small‐scale power. In that study, matching spectral shapes were simultaneously seen in FAC structuring as measured in situ by a Swarm satellite, leading the authors to conclude that FAC structuring was driving the E‐region tracer echoes.…”