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Space Vehicles Directorate, Air Force Research Laboratory, Hanscom Air Force Base, Massachusetts, USA
2 results
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- PublicationRestrictedTurbulent times in the northern polar ionosphere?(2010-04-30)
; ; ; ; ; ; ;Burston, R.; University of Bath, Bath, United Kingdom ;Astin, I.; University of Bath, Bath, United Kingdom ;Mitchell, C.; University of Bath, Bath, United Kingdom ;Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pedersen, T.; Space Vehicles Directorate, Air Force Research Laboratory, Hanscom Air Force Base, Massachusetts, USA ;Skone, S.; Department of Geomatics Engineering, Schulich School of Engineering, University of Calgary, Calgary, Canada; ; ; ; ; A model is presented of the growth rate of turbulently generated irregularities in the electron concentration of northern polar cap plasma patches. The turbulence is generated by the short‐term fluctuations in the electric field imposed on the polar cap ionosphere by electric field mapping from the magnetosphere. The model uses an ionospheric imaging algorithm to specify the state of the ionosphere throughout. The growth rates are used to estimate mean amplitudes for the irregularities, and these mean amplitudes are compared with observations of the scintillation indices S4 and s by calculating the linear correlation coefficients between them. The scintillation data are recorded by GPS L1 band receivers stationed at high northern latitudes. A total of 13 days are analyzed, covering four separate magnetic storm periods. These results are compared with those from a similar model of the gradient drift instability (GDI) growth rate. Overall, the results show better correlation between the GDI process and the scintillation indices than for the turbulence process and the scintillation indices. Two storms, however, show approximately equally good correlations for both processes, indicating that there might be times when the turbulence process of irregularity formation on plasma patches may be the controlling one.186 18 - PublicationRestrictedCorrelation between scintillation indices and gradient drift wave amplitudes in the northern polar ionosphere(2009-07-21)
; ; ; ; ; ; ;Burston, R.; Department of Electronic and Electrical Engineering; Department of Electronic and Electrical Engineering, University of Bath, Bath, UK. ;Astin, I.; Department of Electronic and Electrical Engineering, University of Bath, Bath, UK. ;Mitchell, C.; Department of Electronic and Electrical Engineering, University of Bath, Bath, UK. ;Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pedersen, T.; Space Vehicles Directorate, Air Force Research Laboratory, Hanscom Air Force Base, Massachusetts, USA ;Skone, S.; Department of Geomatics Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada; ; ; ; ; A model is developed of the gradient drift instability growth rate in the north polar cap ionosphere, utilizing a novel approach employing an ionospheric imaging algorithm. The growth rate values calculated by this model are in turn used to estimate how the amplitudes of actual gradient drift waves vary over time as the plasma drifts and the growth rates change with time. Ionospheric imaging is again used in order to determine plasma drift velocities. The final output from the model is in turn used to assess the linear correlation between the scintillation indices S4 and σØ recorded by several GPS L1 band scintillation receivers stationed in the north polar cap and mean gradient drift wave amplitudes. Four separate magnetic storm periods, totaling 13 days, are analyzed in this way. The results show weak but significant linear correlations between the mean wave amplitudes calculated and the observed scintillation indices at F layer altitudes.425 37