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Carrano C.S.,Boston College | Groves K.M.,Air Force Research Lab | Caton R.G.,Air Force Research Lab | Rino C.L.,Rino Consulting | Straus P.R.,The Aerospace Corporation
Radio Science | Year: 2011

We present the Radio Occultation Scintillation Simulator (ROSS), which uses the multiple phase screen method (MPS) to simulate the forward scatter of radio waves by irregularities in the equatorial ionosphere during radio occultation experiments. ROSS simulates propagation through equatorial plasma bubbles which are modeled as homogeneous electron density fluctuations modulated by a Chapman profile in altitude and a Gaussian window in the magnetic east-west direction. We adjust the parameters of the density model using electron density profiles derived from the ALTAIR incoherent scatter radar (9.4N, 167.5E, 4.3 north dip), and space-to-ground observations of scintillation using VHF and GPS receivers that are colocated with the radar. We compare the simulated occultation scintillation to observations of scintillation from the CORISS instrument onboard the C/NOFS satellite during a radio occultation occurring near ALTAIR on 21 April 2009. The ratio of MPS predicted S4 to CORISS observed S4 throughout the F region altitudes of 240-350 km ranged between 0.86 and 1.14. Copyright 2011 by the American Geophysical Union. Source

Rino C.L.,Rino Consulting | Carrano C.S.,Boston College
Radio Science | Year: 2011

Modeling Beacon satellite scintillation data presents a number of challenges. The dominant ionospheric structure is anisotropic, and it evolves nonuniformly. Moreover, the length and the orientation of the propagation path that intercepts the structure vary continuously. Thus, even under ideal observing conditions, it is difficult to extract unambiguous driving-point conditions from single-receiver or multireceiver observations. Statistical models are invariably used to interpret scintillation measurements, but the statistical models themselves require a high degree of statistical uniformity that applies only to segments of the data. These challenges are well known, but evolving computer capabilities have provided new opportunities. Modern computer resources support high-fidelity simulations that capture the three-dimensional propagation phenomena in representative propagation environments. Because all aspects of such simulations are known or measurable, one can validate theoretical assumptions and the effectiveness of various analysis procedures. This paper reviews the theory and illustrates the numerical simulation it supports. Copyright 2011 by the American Geophysical Union. Source

Deshpande K.B.,Virginia Polytechnic Institute and State University | Bust G.S.,Johns Hopkins University | Clauer C.R.,Virginia Polytechnic Institute and State University | Rino C.L.,Rino Consulting | Carrano C.S.,Boston College
Journal of Geophysical Research: Space Physics | Year: 2014

Complex magnetosphere-ionosphere coupling mechanisms result in high-latitude irregularities that are difficult to characterize using only Global Navigation Satellite System (GNSS) scintillation measurements. However, GNSS observations combined with physical parameters derived from modeling can be used to study the physics of these irregularities. We have developed a full three-dimensional electromagnetic wave propagation model called "Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere" (SIGMA), to simulate GNSS scintillations. This model eliminates the most significant approximation made by the previous simulation approaches about the correlation length of the irregularity. Thus, for the first time, using SIGMA, we can accomplish scintillation simulations of significantly high fidelity. While the model is global, it is particularly applicable at high latitudes as it accounts for the complicated geometry of the magnetic field lines in these regions. Using SIGMA, we simulate the spatial and temporal variations in the GNSS signal phase and amplitude on the ground. In this paper, we present the model and results from a study to determine the sensitivity of the SIGMA outputs to different input parameters. We have deduced from our sensitivity study that the peak to peak (P2P) power gets most affected by the spectral index and line of sight direction, while the P2P phase and standard deviation of the phase (σφ) are more sensitive to the anisotropy of the irregularity. The sensitivity study of SIGMA narrows the parametric space to investigate when comparing the modeled results to the observations. Key Points We present a global GNSS scintillation model with significantly high fidelity Using SIGMA, we can study intermediate-scale irregularities at high latitudes Sensitivity study would help when comparing with observations (follow-up paper) ©2014. American Geophysical Union. All Rights Reserved. Source

Carrano C.S.,Boston College | Rino C.L.,Rino Consulting
Proceedings - 2011 International Conference on Electromagnetics in Advanced Applications, ICEAA'11 | Year: 2011

We solve the 4th moment equation for propagation through an extended random medium using the split-step technique. The statistics of ionospheric variations are specified in terms of a structure function consistent with Rino's power law phase screen model (1979). Solutions of the 4th moment equation are not limited to the weak scatter or asymptotically strong scatter regimes; they are valid over the full range of geophysically observed conditions. We compare numerical results with observations of GPS (L band) scintillations acquired at Ascension Island (7.96°S, 14.41°W) during the previous solar maximum. We demonstrate that accurate predictions of the decorrelation time require proper treatment of the propagation geometry and rate at which the ray path scans through the drifting plasma irregularities. © 2011 IEEE. Source

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