Response of High-Latitude GNSS Scintillations to Ionospheric Gradients and Particle Precipitation During Storms and Substorms

Le résumé fourni par la source

Global Navigation Satellite System (GNSS) signals are highly susceptible to ionospheric scintillations, which can degrade positioning accuracy by several meters even under mild conditions and can cause total signal loss during periods of strong geomagnetic activity. High-latitude regions are particularly affected due to enhanced particle precipitation and strong ionospheric convection, making these areas critical for both operational navigation systems and space weather forecasting. This study examines the response of global scintillations during geomagnetic storms and substorms, using eight years (2013–2021) of amplitude (S4) and phase ($\sigma_{\phi}$) measurements from the Canadian High Arctic Ionospheric Network (CHAIN), providing extensive coverage across multiple geomagnetic latitudes and local times. We find that scintillation response is largest during the storm main phase and the substorm expansion phase, highlighting the key role of transient geomagnetic activity. The analysis considers all storm and substorm phases to characterize how temporal and spatial gradients of total electron content (TEC), together with particle precipitation, are linked to scintillations. Statistical analysis, considering response times up to one hour after storm and substorm onsets, reveals significant correlations between TEC gradients and the $\sigma_{\phi}$ index, particularly near dawn and noon magnetic local time at 70° magnetic latitude. The response shifts poleward with increasing response time and exhibits discernible dawn–dusk asymmetries. In addition, a persistent response develops in the convection throat, becoming noticeable after 10 minutes and possibly associated with polar cap patches and cusp precipitation. Enhancement of scintillations is also observed at premidnight, likely associated with monoenergetic electron precipitation. The observed density fluctuations that drive scintillations are likely generated by gradient drift instabilities in regions of strong convection, with Kelvin–Helmholtz instabilities potentially contributing in areas of strong flow shear. The spatial distribution further suggests that diffuse electron precipitation contributes to dawn–dusk asymmetries, whereas enhanced electron density in the convection throat during storms likely drives the noon response. By systematically linking TEC gradients, particle precipitation, and observed scintillation responses, this study provides new insight into the physical mechanisms controlling GNSS signal disturbances at high latitudes and their temporal evolution, with implications for both operational navigation systems and predictive space weather modeling.

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