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3D Spatial and Temporal Analysis of Ionosphere Electron Density Using Iranian Permanent GPS Network (IPGN)
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M. R. Ghaffari Razin *   , B. Voosoghi |
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Abstract: (8733 Views) |
| The ionosphere is the part of the atmosphere in which the number of free electrons is so high that it significantly affects the propagation of radio waves. Since the deactivation of SA, the accuracy of the differential positioning with GPS is mostly dominated by the refraction delay of the GPS carrier waves in Ionosphere. To improve the accuracy of real time positions, it is customary to use the existing models in order to account for various sources of errors, including the effect of Ionosphere. Application of the single layer model, in which the electron content of Ionosphere is assumed to be condensed on a thin shell at a specific height, is a well established technique to account for the ionosphere delay.In contrary to this model, multi-layer modeling can provide three-dimensional information on the spatial distribution of the electrons in atmosphere. In this method, spherical harmonics and empirical orthogonal functions are the base functions in use for modeling the horizontal and the vertical content of the electron density. This is at the cost of using regularization techniques for solving the corresponding problem. Therefore, the developed model should be calibrated, i.e. the corresponding regularization parameter should be chosen, based on the a-priori information of the electron content. In this study, a 3D-modeling of the electron content has been constructed using the GPS measurements over Iran. The Ionosonde Data in the Tehran station (φ=50.64, λ=35.87) have been used for choosing an optimum value for the regularization parameter. To apply the method for constructing a 3D-image of the electron density, GPS measurements of the Iranian Permanent GPS Network (at 3-day in 2007) has been used. The instability of solution has been numerically analyzed and the Tikhonov method has been used for regularizing the solution. To come up with an optimum regularization parameter, the relative error in the Electron density profile computed from Ionosonde measurements and their 3D model are minimized. The modeling region is between 24 to 40 N and 44 to 64 W. The result of 3D-Model has been compared to that of the International Reference Ionosphere model 2007 (IRI-2007).The result shows that the electron density has 6×1011ele/cm3 diurnal variation and 9 × 1011ele/cm3 seasonal variations especially in winter months. This method could recover 66% to 99% of the ionosphere electron density. |
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| Keywords: Total Electron Contents, Ionosonde, GPS, IRI 2007, regularization parameter |
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Full-Text [PDF 386 kb]
(2642 Downloads)
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Type of Study: Research |
Subject:
Geo&Hydro
Received: 2014/10/6
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