Multiyear Detection, Classification and Hypothesis of Ionospheric Layer Causing GNSS Scintillation

Abstract

Extreme ultra-violet (EUV) radiation partially ionizes the atmosphere from about 50 km altitude and higher. The ionospheric F layer, from about 150 km and up, peaks in density around 350-450 km and is strongly driven by electromagnetic forcing. The E layer from about 85-150 km is driven not only by electrodynamics but also neutral winds due to the higher density of the thermosphere. In addition to having layers, the ionospheric plasma density may be horizontally structured at scale sizes ranging from global down to tens of meters horizontally. The auroral zone has dynamics largely driven by the interaction of the magnetosphere with the ionosphere and thermosphere along the Earth's field lines. In this zone, large scale features can give rise to smaller scale plasma density variations, of order 100 m across. Radio waves propagating through these density variations may undergo fluctuations, known as scintillation, of the signal phase or amplitude when received. Ionospheric scintillation can interrupt radio communications and degrade satellite-based navigation services. Numerous researchers have worked in measuring, modeling, and mitigating scintillation.Scintillation investigations dating back to Aarons (1982) have quantified where in the ionosphere scintillations tend to occur (Basu et al., 1988). The high-latitude and low-latitude zones are understood to have dynamic instabilities that can lead to multi-scale structuring at the scale sizes that affect Global Navigation Satellite System (GNSS) signals such as the Global Positioning System (GPS). Prior to the development of scintillation monitoring receivers, Aarons (1997) used geodetic GPS stations in the auroral latitudes to investigate phase fluctuations associated with scintillations. In the polar zone, Alfonsi et al. (2011) investigated scintillation data in both polar regions for solar minimum year 2008 and noted that the cusp is associated with a significant number of phase scintillations, and that polar cap patches are associated with amplitude or phase scintillations. More recently, interest has grown in the occurrence of mid-latitude scintillations (Mrak et al., 2020). While numerous campaigns with scintillation receivers have been conducted through the years (Jayachandran et al., 2009;Jiao et al., 2013), multi-year studies are valuable for looking at trends with solar cycle. The 11-year solar cycle period is important for determining the amount of solar radiation, particularly ionizing EUV, emitted towards the Earth that influences the global density of the ionosphere as well as transient geomagnetic storms.

Ionospheric plasma structuring in relation to auroral particle precipitation

“…Our findings are in agreement with this, but we however show that more energetic particle precipitation penetrating down to the E-region may be a main source and is found colocated with intense elevated σ ϕ . The link between elevated σ ϕ or phase scintillations and E-region auroral particle precipitation has also been observed by several authors (e.g., Kinrade et al, 2013;Forte et al, 2017;Loucks et al, 2017;Sreenivash et al, 2020;Makarevich et al, 2021;Datta-Barua et al, 2021).…”

Nightside High‐Latitude Phase and Amplitude Scintillation During a Substorm Using 1‐Second Scintillation Indices

“…Although the precise altitude of aurora is unknown, the validity of the altitude was confirmed by comparing the auroral structures at the adjacent ASIs. The same projection altitude was used for the pierce points of the CHAIN data, considering that scintillation in the nightside auroral oval is often seen in the E‐region (Datta‐Barua et al., 2021; Loucks et al., 2017; Makarevich et al., 2021; Semeter et al., 2017). As mentioned above, this mapping altitude assumption does not affect a comparison between the data from the co‐located CHAIN receivers and THEMIS ASIs.…”