GPS Scintillations in the European Arctic Related to the Large-Scale Ionospheric Convection

C.N. Mitchell, G. De Franceschi, L. Alfonsi and M. Lester

Abstract:	The role of the auroral/polar ionosphere in producing small-scale irregularities in electron-concentrations is well known. High-energy particles from the solar-wind can enter the Earth´s ionosphere and create field-aligned irregularities by impact ionisation. Similarly, energetic particles trapped in the tail of Earth’s magnetosphere can be released during magnetospheric storms and substorms creating such irregularities. Such structures create strong gradients in total electron content (TEC) and these gradients can cause rapid phase and amplitude fluctuations in the carrier signal of the radio-waves which pass through them. These events are particularly important when they impact upon satellite-to-ground communication and navigation links. In this work a multi-instrument approach is taken to investigating the scintillations, in order to relate the physical processes through to the impact on a particular system. A GPS Ionospheric Scintillation and TEC Monitor (GISTM) was installed at Ny-Alesund (78.9N, 11.9E,) in September 2003 by INGV, Rome. The GISTM System consisting of a NovAtel OEM4 dual-frequency receiver with special firmware, comprises the major component of a GPS signal monitor, specifically configured to measure and automatically record amplitude and phase scintillation from the L1 frequency GPS signals, and ionospheric TEC from the L1 and L2 frequency GPS signals. In conjunction with scintillation measurements, the Multi-Instrument Data Analysis System (MIDAS, Mitchell and Spencer, 2003) is used to map the ionisation distribution from multiple observations of GPS differential phase. MIDAS is a spatial and temporal algorithm for imaging the atmosphere and ionosphere. This assimilation tool uses dual-frequency observations from the GPS satellites to produce four-dimensional images of electron concentration over very large geographical regions (potentially globally). In this study of the October 2003 storm, the convection of the plasma across the polar-cap, observed indirectly from the apparent movement of huge enhanced regions of TEC, is related to the plasma velocities observed from the SuperDARN radars. It is shown that the regions of the ionosphere causing GPS scintillation can be related to the convection of large-scale enhancements containing small-scale irregularities across the polar cap under these highly disturbed conditions. Origins of the enhanced ionization regions are explored.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	392 - 398
Cite this article:	Mitchell, C.N., De Franceschi, G., Alfonsi, L., Lester, M., "GPS Scintillations in the European Arctic Related to the Large-Scale Ionospheric Convection," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 392-398.
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