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Ruohoniemi, J. M.
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Ruohoniemi, J. M.
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- PublicationOpen AccessSatellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere (SIGMA) II: Inverse modeling with high-latitude observations to deduce irregularity physicsIonospheric scintillation is caused by irregularities in the ionospheric electron density. The characterization of ionospheric irregularities is important to further our understanding of the underlying physics. Our goal is to characterize the intermediate (0.1–10 km) to medium (10–100 km) scale high-latitude irregularities which are likely to produce these scintillations. In this paper, we characterize irregularities observed by Global Navigation Satellite System (GNSS) during a geomagnetically active period on 9 March 2012. For this purpose, along with the measurements, we are using the recently developed model: “Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere” (SIGMA). The model is particularly applicable at high latitudes as it accounts for the complicated geometry of the magnetic field lines in these regions and is presented in an earlier paper. We use an inverse modeling technique to derive irregularity parameters by comparing the high rate (50 Hz) GNSS observations to the modeled outputs. In this investigation, we consider experimental observations from both the northern and southern high latitudes. The results include predominance of phase scintillations compared to amplitude scintillations that imply the presence of larger-scale irregularities of sizes above the Fresnel scale at GPS frequencies, and the spectral index ranges from 2.4 to 4.2 and the RMS number density ranges from 3e11 to 2.3e12 el/m3. The best fits we obtained from our inverse method that considers only weak scattering mostly agree with the observations. Finally, we suggest some improvements in order to facilitate the possibility of accomplishing a unique solution to such inverse problems.
92 45 - PublicationOpen AccessGPS phase scintillation at high latitudes during geomagnetic storms of 7–17 March 2012 – Part 2: Interhemispheric comparison(2015)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Prikryl, P.; Geomagnetic Laboratory, Natural Resources Canada, Ottawa, ON, Canada ;Ghoddousi-Fard, R.; Canadian Geodetic Survey, Natural Resources Canada, Ottawa, ON, Canada ;Spogli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Mitchell, C. N.; Department of Electronic and Electrical Engineering, University of Bath, Bath, UK ;Li, G.; Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China ;Ning, B.; Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China ;Cilliers, P. J.; Space Science Directorate, South African National Space Agency, Hermanus, South Africa ;Sreeja, V.; Nottingham Geospatial Institute, University of Nottingham, Nottingham, UK ;Aquino, M.; Nottingham Geospatial Institute, University of Nottingham, Nottingham, UK ;Terkildsen, M.; IPS Radio and Space Services, Bureau of Meteorology, Haymarket, NSW, Australia ;Jayachandran, P. T.; Physics Department, University of New Brunswick, Fredericton, NB, Canada ;Jiao, Y.; Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, USA ;Morton, Y. T.; Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, USA ;Ruohoniemi, J. M.; Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, USA ;Thomas, E. G.; Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, USA ;Zhang, Y; Johns Hopkins University Applied Physics Lab, Laurel, MD, USA ;Weatherwax, A. T.; Department of Physics and Astronomy, Siena College, Loudonville, NY, USA ;Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;De Franceschi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; During the ascending phase of solar cycle 24, a series of interplanetary coronal mass ejections (ICMEs) in the period 7–17 March 2012 caused geomagnetic storms that strongly affected high-latitude ionosphere in the Northern and Southern Hemisphere. GPS phase scintillation was observed at northern and southern high latitudes by arrays of GPS ionospheric scintillation and TEC monitors (GISTMs) and geodetic-quality GPS receivers sampling at 1 Hz. Mapped as a function of magnetic latitude and magnetic local time (MLT), the scintillation was observed in the ionospheric cusp, the tongue of ionization fragmented into patches, sun-aligned arcs in the polar cap, and nightside auroral oval and subauroral latitudes. Complementing a companion paper (Prikryl et al., 2015a) that focuses on the highlatitude ionospheric response to variable solar wind in the North American sector, interhemispheric comparison reveals commonalities as well as differences and asymmetries between the northern and southern high latitudes, as a consequence of the coupling between the solar wind and magnetosphere. The interhemispheric asymmetries are caused by the dawn–dusk component of the interplanetary magnetic field controlling the MLT of the cusp entry of the storm-enhanced density plasma into the polar cap and the orientation relative to the noon–midnight meridian of the tongue of ionization.716 565