Identification of scintillation signatures on GPS signals originating from plasma structures detected with EISCAT incoherent scatter radar along the same line of sight.

Biagio Forte,Chris Coleman,Federico Da Dalt,Susan Skone,Tommaso Panicciari,Joe Kinrade,Ingemar Häggström,Cathryn Mitchell,Gary Bust

doi:10.1002/2016ja023271

Abstract

Ionospheric scintillation originates from the scattering of electromagnetic waves through spatial gradients in the plasma density distribution, drifting across a given propagation direction. Ionospheric scintillation represents a disruptive manifestation of adverse space weather conditions through degradation of the reliability and continuity of satellite telecommunication and navigation systems and services (e.g., European Geostationary Navigation Overlay Service, EGNOS). The purpose of the experiment presented here was to determine the contribution of auroral ionization structures to GPS scintillation. European Incoherent Scatter (EISCAT) measurements were obtained along the same line of sight of a given GPS satellite observed from Tromso and followed by means of the EISCAT UHF radar to causally identify plasma structures that give rise to scintillation on the co‐aligned GPS radio link. Large‐scale structures associated with the poleward edge of the ionospheric trough, with auroral arcs in the nightside auroral oval and with particle precipitation at the onset of a substorm were indeed identified as responsible for enhanced phase scintillation at L band. For the first time it was observed that the observed large‐scale structures did not cascade into smaller‐scale structures, leading to enhanced phase scintillation without amplitude scintillation. More measurements and theory are necessary to understand the mechanism responsible for the inhibition of large‐scale to small‐scale energy cascade and to reproduce the observations. This aspect is fundamental to model the scattering of radio waves propagating through these ionization structures. New insights from this experiment allow a better characterization of the impact that space weather can have on satellite telecommunications and navigation services.

Highlights

The propagation of radio waves through drifting inhomogeneties in the spatial distribution of electron density may lead to degradation of the overall signal manifesting itself as fluctuations of the phase and amplitude components of the radio waves, a phenomena known as scintillation [Yeh and Liu, 1982, Aarons, 1982; Basu et al, 1999; Basu et al, 2001; Fremouw et al, 1978]
The present analysis has identified and quantified for the first time a causal relationship between auroral ionisation structures and scintillation on GPS signals
The EISCAT UHF radar was pointed in the line of sight of a given GPS satellite, the satellite signal being recorded by means of a GPS scintillation monitor co-located with EISCAT UHF transmitter at Tromso

Summary

Introduction

The propagation of radio waves through drifting inhomogeneties in the spatial distribution of electron density may lead to degradation of the overall signal manifesting itself as fluctuations of the phase and amplitude components of the radio waves, a phenomena known as scintillation [Yeh and Liu, 1982, Aarons, 1982; Basu et al, 1999; Basu et al, 2001; Fremouw et al, 1978]. When radio waves scatter through electron density structures the wave energy is scattered away from the original propagation direction, leading to a lower signal being recorded at the receiving antenna. In the case of weak scattering the propagation problem can often be approximated by means of a single phase changing screen containing a distribution of phase changes (as a consequence of variations onto the spatial distribution of the refractive index) to be superimposed on the incident wave front [Booker and MajidiAhi, 1981; Rino, 1979]. In the case of moderate-to-strong scattering the use of multiple phase screens becomes necessary to accommodate larger and cumulative phase variations in response to propagation through electron density structures with greater extent [Knepp, 1983; Uscinski, 1968; Carrano et al, 2011]. The identification and quantification of the contribution from E and F region irregularities to the observed L-band scintillation is provided through the combination of EISCAT and GPS observations under different circumstances

Results

Discussion

Conclusion