In this contribution, optimal ionosphere-free combinations for a modernized triple-frequency global positioning system ~GPS! are derived. It is shown that these ionosphere-free combinations are directly related to the model based on carrier phase observations only, in which the ionospheric delays are estimated. For this model and thus for the ionosphere-free combinations, integer ambiguity esti...

The gas dynamics of interactions of a tenuous ionosphere with movihg satellites and probes that have bearings on the diagnostics of the ionosphere are discussed. Emphasis is on the cases where the body is moving at mesothermal speeds, namely intermediate between the thermal speeds of ions and electrons of the ambient ionosphere. Methods of collision-free plasma kinetics with self-consistent fie...

Several severe ionosphere storms have occurred in recent years that tripped the WAAS storm detector and caused partial WAAS service shutdowns. Under extreme conditions, these spatial gradients can threaten LAAS. In previous work [1-4], a “linear spatial gradient front” model was established and a threat space was extrapolated based on data from the 6 April 2000 ionospheric storm. User vertical ...

We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types of ionospheric echoes are observed, ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes...

We present a statistical study of low frequency fluctuations of electric and magnetic fields, commonly interpreted as Alfvénic activity. The data base consists of six months of electric and magnetic field measurements by the Astrid-2 microsatellite. The occurrence of the events is studied with respect to the location and general activity. Large regions of broadband Alfvénic activity are persist...

Communications have come to rely heavily on ionospheric radio in spite of the sometimes unpredictable behavior of the ionosphere as a transmission medium. Far from being the static reflector of radio waves that the communicator would desire, the ionosphere continuously and sometimes suddenly, undergoes structural changes on almost all scales of size and time. Such changes upset the often delica...

The operation of low frequency SAR sensors on space-borne platforms is perturbed by the presence of Earth’s ionosphere. The purpose of this paper is to outline an initial methodology exploiting the potential of Coherent Scatterers (CSs) for the estimation and correction of the different effects induced by ionospheric disturbances on SAR images. Based on the high spectral correlation and the poi...

Atmospheric scientists need to observe fluctuations in the ionosphere, both to probe the underlying atmospheric physics, and to remove the effects of these fluctuations from other measurements. We have built an FPGA-based, pipelined array processor that allows us to make these observations in real-time, using passive radar techniques. Our array processor time-multiplexes 16 multiply–accumulator...

─ Finite-Difference Time-Domain (FDTD) modeling of electromagnetic wave propagation in the Earth-ionosphere waveguide has gained significant interest over the past two decades. Initially, FDTD modeling capabilities were largely limited to two-dimensional models assuming a plasma ionosphere (but incapable of accounting for Faraday rotation), or to threedimensional global models assuming a simple...

[1] In this paper we investigate how the parameters of the ionosphere and the low-altitude magnetosphere mediate the formation and spatiotemporal properties of small-scale, intense electromagnetic structures commonly observed by low-altitude satellites in the auroral and subauroral magnetosphere. The study is based on numerical modeling of a time-evolving, nonlinear system that describes multis...