Global Positioning System (GPS) Scintillation Associated with a Polar Cap Patch

Jayachandran P Thayyil,David R Themens,Anthony M Mccaffrey,Zanyang Xing,Qinghe Zhang,Benjamin Reid,Christopher Watson,Yong Wang

doi:10.3390/rs13101915

Jayachandran P Thayyil, David R Themens + Show 6 more

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https://doi.org/10.3390/rs13101915

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Abstract

A Global Positioning System (GPS) network in the polar cap, along with ionosonde and SuperDARN radar measurements, are used to study GPS signal amplitude and phase scintillation associated with a polar cap patch. The patch was formed due to a north-to-south transition of the interplanetary magnetic field (IMF Bz). The patch moved antisunward with an average speed of ~600 m/s and lasted for ~2 h. Significant scintillation occurred on the leading edge of the patch, with smaller bursts of scintillation inside and on the trailing edge. As the patch moved, it maintained the integrity of the scintillation, producing irregularities (Fresnel scale) on the leading edge. There were no convection shears or changes in the direction of convection during scintillation events. Observations suggest that scintillation-producing Fresnel scale structures are generated through the non-linear evolution of the gradient drift instability mechanism.

Highlights

Ionospheric scintillation, the stochastic variations observed in the amplitude and phase of a trans-ionospheric radio signal, is generated by Fresnel scale irregularities in the ionosphere [1,2]
We present a case study of Global Positioning System (GPS) signal amplitude and phase scintillation observation associated with a polar cap patch in an attempt to identify the underlying mechanism(s) that generates radio wave scintillation in the polar region
In the F-region, the classical linear-gradient drift instability mechanism requires that density gradients be parallel to the direction of the plasma drift, while the shear instability requires the presence of strong flow shears

Summary

Introduction

Ionospheric scintillation, the stochastic variations observed in the amplitude and phase of a trans-ionospheric radio signal, is generated by Fresnel scale irregularities in the ionosphere [1,2]. Theoretical and numerical simulation studies have shown that these small-scale structures are produced on the trailing edge of convecting polar cap patches through the gradient drift instability and shear instability mechanisms [18,19,35] and penetrate to the leading edge [36] These theories and simulations are still not well tested, and recent observations [25,30] have provided contradictory evidence, as no preferred geometry of the ray paths concerning electric field and gradients for the scintillation occurrence and scintillation occurred on both the leading and trailing edges of patches. Even though times are corrected for the travel time from the upstream solar wind monitor to the magnetopause, the correction has a certain level of uncertainty [41] To avoid this uncertainty, a detectable ionospheric response (e.g., changes in the direction of convection) was taken as the time of arrival of the IMF changes in the ionosphere [42].

The thethe

Discussion

Conclusions