Extremely large ionospheric gradients can pose a potential integrity threat to the users of Local Area Augmentation System (LAAS), and thus the development of an ionospheric anomaly threat model is essential for system design and operation. This paper presents a methodology for long-term ionosphere monitoring which will be used to build an ionosphere threat model, evaluate its validity over the...

The advent of a second civil GPS frequency heralds a new phase of GPS performance. For single-frequency GPS users, the signal delay due to refraction through the ionosphere is the largest and most variable source of positioning error. Dual-frequency users take advantage of the dispersive nature of the ionosphere, combining the GPS observables to eliminate most of this error, on the order of met...

Space based GPS measurements onboard Low Earth Orbiting (LEO) satellites provide a uniquepossibility for exploring the ionosphere on a global scale. Both the radio occultation measurements in thelimb sounding mode and the navigation measurements using a zenith viewing GPS antenna provide theTotal Electron Content (TEC) along numerous ray paths. TEC may effectively be used for re...

With the successful implementation of the Wide Area Augmentation System (WAAS) for the North America, there is interest in implementing similar systems in other parts of the world. The ionosphere over certain parts of the globe, notably equatorial regions and Brazil in particular, can have a far greater impact on the signals received from the satellites. The Ionospheric corrections form an inte...

The signals from VLF/LF transmitters are known to propagate in the Earth-ionosphere waveguide, so that the subionospheric propagation characteristics are very sensitive to the condition of the lower ionosphere. We know that there appear the terminator times just around the sunrise and sunset in the diurnal variation of subionospheric VLF/LF signal (amplitude and phase). These terminator times a...

[1] The results presented in this paper provide an explanation for electromagnetic oscillations with frequencies much less than the fundamental eigenfrequency of the magnetosphere measured in the regions where the ionospheric conductivity is low and a small-amplitude, large-scale electric field in the ionosphere exists. This study is based on numerical simulations of a reduced two-fluid MHD mod...

Abeiraet-We have studied the extent to which certain transport processes affect ion composition and heat flow in the daytime, topside Venus ionosphere. Particular attention is given to the conditions that prevailed during the Mariner 5 measurements, at which time the topside Venus ionosphere appeared to be in a state of diffusive equilibrium. We have found that the ion composition is sensitive ...

[1] Data Interpolating Empirical Orthogonal Functions (DINEOFs) are a data-based method for determining a few orthogonal basis functions that optimally reproduce a given data set. This technique is applied to meridional drift measurements performed by the Coupled Ion Neutral Dynamics Investigation (CINDI) onboard the Communication/Navigation Outage Forecasting System (C/NOFS) as well as electro...

Solar radiations affect the total electron content of the ionosphere that may disturb the radio-frequencies used in telecommunications. It may state with full confidence that the increase in the critical frequencies of the F2 layer from the values observed in the morning hours to the afternoon maximum frequencies, is due to ultraviolet (UV) radiation from the Sun. During an ionospheric storm, s...

There is some intriguing research about whether large magnitude earthquakes are associated with ionospheric changes caused by electromagnetic signals released by the crushing of rock and their crystalline structures. If so then ionospheric changes might be a mechanism for major earthquake prediction. Prior to some recent quakes, scientists have detected electromagnetic and other disturbances in...